Question

ffffind the unknown angles sssstepwise

Answer 1

It is given that AB = AC

So, a = b

By Angle Sum Property,

a + b + 42° = 180°

» a + a = 180 - 42 [a = b so replace it]

» 2a = 138°

» a = 69°

So, b = 69°

And c = 180° - b [Linear Pair]

» c = 180 - 69

» c = 111°

Or

c = 42° + a [Sum of opposite interior angles is equal to exterior angle]

» c = 42 + 69

» c = 111°