Question

∆abc is isosceles with ab=ac,if a=80° .What is the measure of b

Answer 1

Given,

ab=ac

=>angle acb=angle abc (Angle opposite to equal sides are equal)

Let angle abc be X.

Therefore,

Angle a=80°

Angle b=x°

Angle c=x°

We know,

Sum of the interior angles of a triangle = 180°

=> angle a + angle b + angle c = 180°

=> 80° + x° + x° = 180°

=> 80° + 2x° = 180°

=> 2x° = (180-80)°

=> 2x° = 100°

=> x° = (100/2)°

=> x = 50°

Therefore,

The measure of b is 50°.