Question

In triangle ABC, angle A = (4x+5) and angle B = (5x-1)

What is angle C?

29

180

8

122

Answer 1

It is an isosceles triangle, therefore


`m\angle A=m\angle B`


`4x+5=5x-1\ \ \ |-5\\4x=5x-6\ \ \ |-5x\\-x=-6\to x=6`


`m\angle A=m\angle B=4\cdot6+5=24+5=29^o`

We know:


`m\angle A+m\angle B+m\angle C=180^o`

therefore


`29^o+29^o+m\angle C=180^o\\\\58^o+m\angle C=180^o\ \ \ |-58^o\\\\m\angle C=122^o`