5 Simple Angle Rules

This lesson covers:

  1. The 5 basic angle rules, namely:
  2. Angles in a triangle add to 180°
  3. Isosceles triangles have 2 equal sides and 2 equal angles 
  4. Angles in a circle add to 360°
  5. Angles in a quadrilateral add to 360°
Triangle with angles 72 degrees, 26 degrees, and missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

82

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Triangle with angles 67 degrees, 83 degrees, and missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

30

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Diagram of a right triangle with a missing angle x and an angle of 33 degrees.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

57

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Diagram of a right-angled triangle with one angle marked as 49 degrees and another angle marked as x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

41

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Diagram of a parallelogram with one angle marked as 100 degrees and another angle marked as x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

80

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Diagram of a parallelogram with angles marked, including one missing angle labeled x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

63

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Diagram of a triangle with a 30 degree angle and a missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

75

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Diagram of a triangle with a missing angle x and one angle labeled as 68 degrees.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

44

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Diagram showing a circle divided into three segments with angles 130 degrees, 80 degrees, and x degrees.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

150

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Diagram showing a circle with an angle of 60 degrees and a missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

210

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Diagram showing a semicircle with a 55-degree angle and a missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

125

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Illustration showing a semicircle with a 159 degree angle and missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

21

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Diagram showing a shape with angles labeled 100 degrees, 55 degrees, and x. The task is to find the missing angle x.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

75

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Diagram showing a geometric shape with angles 79 degrees, 64 degrees, and x to find the missing angle.

Find the missing angle, x.

(Shapes are NOT drawn accurately)

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