Angles, symmetry and 2-D shapes

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선생님을 위해: Angles, symmetry and 2-D shapes(Primary Maths, Grade 4)을(를) 위한 바로 쓸 수 있는 수업 슬라이드, 복습 노트 — 수업에 사용하거나, 학생들이 실시간 게임으로 즐기는 인터랙티브 클래스 활동으로 진행하세요.

수업 노트

Points, Lines, and Angles

A point is an exact spot. We name it with a capital letter, like point A.
A line is straight and goes on forever in both directions. We write it as line AB.
A line segment is part of a line with two endpoints. It does not go on forever.
A ray has one endpoint and goes on forever in one direction.
An angle is formed when two rays meet at a point. The shared point is the vertex.
The two rays are called the sides of the angle. We write an angle as ∠ABC, where B is the vertex.

Measuring Angles

We measure angles in degrees using the symbol °.
A full turn around a point is 360°.
A right angle is exactly 90°. It looks like the corner of a square.
An acute angle is less than 90°. It is smaller than a right angle.
An obtuse angle is more than 90° but less than 180°. It is bigger than a right angle.
A straight angle is exactly 180°. It forms a straight line.

Parallel and Perpendicular Lines

Parallel lines are lines that never meet. They stay the same distance apart.
We write parallel lines like AB ∥ CD.
Perpendicular lines meet at a right angle (90°).
We write perpendicular lines like AB ⊥ CD.
You can find perpendicular lines at the corners of a rectangle.

Triangles

A triangle is a 2-D shape with 3 sides and 3 angles.
Triangles can be named by their sides: equilateral (all sides equal), isosceles (two sides equal), and scalene (no sides equal).
Triangles can also be named by their angles: acute (all angles acute), right (one right angle), and obtuse (one obtuse angle).
The angles inside any triangle add up to 180°.
An equilateral triangle is also acute because all its angles are 60°.

Quadrilaterals

A quadrilateral is a 2-D shape with 4 sides and 4 angles.
The angles inside any quadrilateral add up to 360°.
A square has 4 equal sides and 4 right angles.
A rectangle has 2 pairs of equal sides and 4 right angles.
A parallelogram has 2 pairs of parallel sides. Opposite sides are equal.
A rhombus has 4 equal sides, but its angles are not necessarily right angles.
A trapezoid has only 1 pair of parallel sides.

Symmetry

A shape has symmetry if you can fold it in half so the two halves match exactly.
The fold line is called the line of symmetry.
A square has 4 lines of symmetry.
A rectangle has 2 lines of symmetry.
An equilateral triangle has 3 lines of symmetry.
A circle has infinite lines of symmetry.
To complete a symmetric figure, draw the mirror image on the other side of the line.

Coordinates and Translations

We use coordinates to describe positions on a grid. They are written as (x, y).
The first number is the x-coordinate (how far across).
The second number is the y-coordinate (how far up).
The point (0,0) is called the origin.
A translation is a slide. The shape moves without turning or flipping.
To translate a shape, move every point the same distance in the same direction.
For example, moving a shape 3 squares right and 2 squares up is a translation.

슬라이드

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연습 문제

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1.What is the name of the point where two rays meet to form an angle?
Easy
- Avertex
- Bside
- Cedge
- Dcorner
2.Which of the following is a straight angle?
Easy
- A90°
- B180°
- C360°
- D45°
3.An acute angle is greater than 90°.
Easy
True or false?
4.Which of the following angles is obtuse?
Easy
- A35°
- B90°
- C120°
- D180°
5.What is the measure of angle BAC if angle BAD = 30° and angle DAC = 45°?
Medium
- A75°
- B15°
- C60°
- D90°
6.Which of the following are types of angles? (Select all that apply)
Medium
- Aacute
- Bobtuse
- Cparallel
- Dright
7.Match each angle type with its measure.
Medium
- right angle
- acute angle
- straight angle
- 90°
- less than 90°
- 180°
8.Put these angles in order from smallest to largest: 90°, 45°, 180°, 120°.
Medium
- 45°
- 90°
- 120°
- 180°

더 많은 문제

9.Match each angle type with its correct measure.
Easy
- Right angle
- Straight angle
- Acute angle
- 90°
- 180°
- less than 90°
10.Put these angles in order from smallest to largest: 120°, 45°, 180°, 90°.
Medium
- 120°
- 45°
- 180°
- 90°
11.In the figure, ∠BAD = 30° and ∠DAC = 45°. What is the measure of ∠BAC?
Medium
- A75°
- B15°
- C60°
- D90°
12.Which of these shapes has exactly one line of symmetry?
Medium
- AIsosceles triangle
- BEquilateral triangle
- CRectangle
- DSquare
13.Which of the following are quadrilaterals? (Select all that apply)
Medium
- ASquare
- BTriangle
- CRectangle
- DPentagon
- EParallelogram
14.Match each shape with its number of lines of symmetry.
Medium
- Square
- Rectangle
- Equilateral triangle
- 4
- 2
- 3
15.Put these shapes in order by number of lines of symmetry, from fewest to most: square, isosceles triangle, rectangle, equilateral triangle.
Medium
- Square
- Isosceles triangle
- Rectangle
- Equilateral triangle
16.A parallelogram always has a line of symmetry.
Medium
True or false?
17.Which of the following triangles has all three sides equal?
Medium
- AEquilateral
- BIsosceles
- CScalene
- DRight
18.What type of triangle has exactly two equal sides?
Medium
- AIsosceles
- BEquilateral
- CScalene
- DObtuse
19.Which of the following are types of triangles? (Select all that apply)
Medium
- AAcute
- BScalene
- CParallel
- DRight
- EObtuse
20.Which of the following is NOT a quadrilateral?
Hard
- ATrapezoid
- BRhombus
- CHexagon
- DParallelogram
21.A shape has 4 sides and 4 right angles. Which shape could it be?
Hard
- ASquare
- BTrapezoid
- CRhombus
- DParallelogram
22.A rectangle has four lines of symmetry.
Easy
True or false?
23.Sort these angles by size, from smallest to largest: obtuse, acute, right, straight.
Medium
- Obtuse
- Acute
- Right
- Straight
24.Match each type of triangle with its defining property.
Hard
- Equilateral
- Isosceles
- Scalene
- All sides equal
- Two sides equal
- No sides equal
25.Which of the following statements is true about a rhombus?
Hard
- AIt has four right angles.
- BAll four sides are equal.
- CIt has exactly one pair of parallel sides.
- DIt has no lines of symmetry.
26.A shape has exactly two lines of symmetry and four right angles. Which shape is it?
Challenge
- ARectangle
- BSquare
- CRhombus
- DParallelogram
27.Which of the following angles is acute?
Medium
- A35°
- B90°
- C120°
- D180°
28.Which of the following are true about a square? (Select all that apply)
Medium
- AAll sides are equal.
- BIt has four right angles.
- CIt has four lines of symmetry.
- DIt is a type of triangle.
29.An obtuse angle is smaller than a right angle.
Medium
True or false?
30.Sort these quadrilaterals by number of lines of symmetry, from fewest to most: rectangle, square, trapezoid, rhombus.
Hard
- Rectangle
- Square
- Trapezoid
- Rhombus
31.Match each angle type with its measurement range.
Hard
- Acute
- Obtuse
- Reflex
- less than 90°
- between 90° and 180°
- between 180° and 360°
32.Which of the following is a reflex angle?
Hard
- A200°
- B90°
- C180°
- D120°
33.Which of the following shapes has exactly one pair of parallel sides?
Hard
- ATrapezoid
- BRectangle
- CSquare
- DParallelogram
34.Which of the following are true about a parallelogram? (Select all that apply)
Hard
- AIt has two pairs of parallel sides.
- BOpposite sides are equal.
- CIt always has four right angles.
- DIt is a quadrilateral.
35.A rhombus is a type of parallelogram.
Medium
True or false?
36.Sort these angles by size, from smallest to largest: reflex, straight, acute, obtuse.
Hard
- Reflex
- Straight
- Acute
- Obtuse
37.Match each shape with its number of sides.
Hard
- Triangle
- Quadrilateral
- Pentagon
- 3
- 4
- 5
38.Which of the following is NOT a parallelogram?
Hard
- ARectangle
- BRhombus
- CTrapezoid
- DSquare
39.Which of the following shapes has the most lines of symmetry?
Challenge
- ASquare
- BRectangle
- CEquilateral triangle
- DRegular hexagon
40.Which of the following are true about a rectangle? (Select all that apply)
Hard
- AIt has four right angles.
- BOpposite sides are equal.
- CIt has two lines of symmetry.
- DAll sides are equal.
41.Complete the sentence.
Easy
A right angle measures ____ degrees.
42.How many degrees are in a full turn?
Easy
43.What is the name of the angle that is greater than 180° but less than 360°?
Medium
44.Complete the sentence: An angle that measures exactly 90° is called a ___ angle.
Medium
An angle that measures exactly 90° is called a ____ angle.
45.A triangle has angles 50° and 60°. What is the measure of the third angle?
Medium
46.Complete the sentence: A shape that can be folded along a line so that the two halves match exactly has a line of ___.
Medium
A shape that can be folded along a line so that the two halves match exactly has a line of ____.
47.A quadrilateral has angles 90°, 90°, and 120°. What is the measure of the fourth angle?
Hard
48.What is the name for a line that divides a shape into two mirror-image halves?
Medium
49.Complete the sentence: A triangle with no equal sides is called a ___ triangle.
Medium
A triangle with no equal sides is called a ____ triangle.
50.The angle between the two hands of a clock at 3:00 is how many degrees?
Hard
51.Complete the sentence: The point where two sides of a polygon meet is called a ___.
Medium
The point where two sides of a polygon meet is called a ____.
52.A regular pentagon has how many lines of symmetry?
Hard
53.Explain why a triangle can have at most one right angle.
Medium
54.How many degrees are in a full turn?
Easy
- A432 °
- B360 °
- C324 °
- D396 °
55.A triangle has angles 50° and 60°. What is the measure of the third angle?
Medium
- A77 °
- B63 °
- C84 °
- D70 °
56.A quadrilateral has angles 90°, 90°, and 120°. What is the measure of the fourth angle?
Hard
- A66 °
- B60 °
- C54 °
- D72 °
57.The angle between the two hands of a clock at 3:00 is how many degrees?
Hard
- A108 °
- B81 °
- C99 °
- D90 °
58.A regular pentagon has how many lines of symmetry?
Hard
- A4
- B7
- C5
- D6

복습 노트

## Angles, Symmetry and 2-D Shapes – Revision Notes ### Angles - An **angle** is formed when two lines meet at a point. The lines are called **sides**, and the meeting point is the **vertex**. - Angles are measured in **degrees** (°). A full turn is 360°. - **Types of angles:** - **Acute angle**: less than 90° (smaller than a right angle). - **Right angle**: exactly 90° (a quarter turn). - **Obtuse angle**: between 90° and 180° (bigger than a right angle but less than a straight line). - **Straight angle**: exactly 180° (a half turn). - **Reflex angle**: between 180° and 360° (more than a straight angle). - **Angle addition**: If a point lies inside an angle, the whole angle equals the sum of the two smaller angles. For example, if D is inside ∠BAC, then m∠BAC = m∠BAD + m∠DAC. ### Lines and Points - **Point**: an exact location. - **Line**: a straight path that goes on forever in both directions. - **Line segment**: part of a line with two endpoints. - **Ray**: part of a line with one endpoint, going on forever in one direction. - **Parallel lines**: lines that never meet, always the same distance apart. - **Perpendicular lines**: lines that meet at a right angle (90°). ### 2-D Shapes - **Triangle**: a shape with 3 sides and 3 angles. - By sides: **equilateral** (all sides equal), **isosceles** (two sides equal), **scalene** (no sides equal). - By angles: **acute** (all angles acute), **right** (one right angle), **obtuse** (one obtuse angle). - **Quadrilateral**: a shape with 4 sides and 4 angles. - Examples: square, rectangle, parallelogram, rhombus, trapezoid. ### Symmetry - A **line of symmetry** divides a shape into two matching halves that are mirror images. - Some shapes have one or more lines of symmetry; others have none. - To complete a symmetric figure, reflect the given part across the line of symmetry. ### Coordinates and Translations - A **coordinate grid** uses two numbers to show a position: (x, y). The first number is the horizontal position (x-coordinate), the second is the vertical position (y-coordinate). - A **translation** moves a shape without rotating or flipping it. It slides left/right and up/down. ### Key Formulas - Angle addition: m∠BAC = m∠BAD + m∠DAC (if D is inside ∠BAC). - Full turn = 360°, half turn = 180°, quarter turn = 90°. Remember: Practice identifying angles and shapes, and always check for symmetry!

Angle: A figure formed by two lines that meet at a point. The lines are called sides, and the meeting point is the vertex.
Vertex: The point where two lines meet to form an angle.
Degree: A unit for measuring angles. A full turn is 360 degrees.
Acute angle: An angle less than 90 degrees.
Right angle: An angle exactly 90 degrees.
Obtuse angle: An angle between 90 and 180 degrees.
Straight angle: An angle exactly 180 degrees.
Reflex angle: An angle between 180 and 360 degrees.
Line: A straight path that goes on forever in both directions.
Line segment: Part of a line with two endpoints.
Ray: Part of a line with one endpoint, going on forever in one direction.
Parallel lines: Lines that never meet and are always the same distance apart.
Perpendicular lines: Lines that meet at a right angle (90 degrees).
Triangle: A 2-D shape with three sides and three angles.
Quadrilateral: A 2-D shape with four sides and four angles.
Line of symmetry: A line that divides a shape into two matching halves that are mirror images.
Coordinate grid: A grid used to locate points using two numbers (x, y).
Translation: Moving a shape without rotating or flipping it; sliding it left/right and up/down.

플래시카드

What is an angle?

An angle is formed by two lines that meet at a point. The lines are called sides, and the meeting point is the vertex.

What is the vertex of an angle?

The vertex is the point where the two sides of an angle meet.

What is a right angle?

A right angle measures exactly 90°. It looks like the corner of a square.

What is an acute angle?

An acute angle is smaller than a right angle. It measures less than 90°.

What is an obtuse angle?

An obtuse angle is larger than a right angle but smaller than a straight angle. It measures between 90° and 180°.

What is a straight angle?

A straight angle measures exactly 180°. It looks like a straight line.

What is a reflex angle?

A reflex angle is larger than a straight angle but less than a full turn. It measures between 180° and 360°.

How many degrees are in a full turn?

A full turn is 360°. It is also called a full angle.

What is a line segment?

A line segment is a straight part of a line with two endpoints. It does not go on forever.

What is a ray?

A ray has one endpoint and goes on forever in one direction. It is like a half-line.

What are parallel lines?

Parallel lines are lines that never meet. They are always the same distance apart.

What are perpendicular lines?

Perpendicular lines meet at a right angle (90°). They form a square corner.

How do you name an angle using three letters?

Use three points: one on each side and the vertex in the middle. For example, ∠BAC has vertex A.

What is the angle addition postulate?

If a point D is inside an angle, then the measure of the whole angle equals the sum of the two smaller angles. For example, m∠BAC = m∠BAD + m∠DAC.

What is a triangle?

A triangle is a 2-D shape with three sides and three angles. The sum of its angles is always 180°.

What is an equilateral triangle?

An equilateral triangle has all three sides equal and all three angles equal (each 60°).

What is an isosceles triangle?

An isosceles triangle has two equal sides and two equal angles.

What is a scalene triangle?

A scalene triangle has all sides different lengths and all angles different sizes.

What is a right triangle?

A right triangle has one right angle (90°).

What is a quadrilateral?

A quadrilateral is a 2-D shape with four sides and four angles. The sum of its angles is always 360°.

What is a rectangle?

A rectangle is a quadrilateral with four right angles. Opposite sides are equal and parallel.

What is a square?

A square is a rectangle with all four sides equal. It has four right angles.

What is a parallelogram?

A parallelogram is a quadrilateral with opposite sides parallel and equal in length.

What is a line of symmetry?

A line of symmetry divides a shape into two matching halves that are mirror images. If you fold along the line, the halves match exactly.

How do you find the number of lines of symmetry in a square?

A square has 4 lines of symmetry: two through opposite corners and two through the midpoints of opposite sides.

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