Question

Find the unknown angles in the given figures:

Answer 1

Step 1: Form relations between a and b and solve for them

As given triangle is an isosceles,

∴ a = b

[∵ Angles opposite to equal sides are equal]

a + b + 80° = 180°

[∵ Angle sum property of triangle]

⇒ a + a = 180°- 80°

2a = 100°

a = 50°

∴ a = b = 50°

Step 2: Find x using exterior angle property

x = 80° + a

[∵ Exterior angle property]

⇒ x = 80° + 50°

⇒ x = 130°

Hence, the value of a = 50°, b = 50° and x = 130°.