Question

Question #e355e

Answer 1

`y=40^@`

Explanation:

Given that `AB=AC and angleC=40^@, => DeltaABC` is an isosceles triangle.

An isosceles triangle is a triangle that has two sides of equal length.
The unequal side of an isosceles triangle is usually referred to as the 'base' of the triangle. In the figure, `BC` is the base.
The base angles of an isosceles triangle are always equal. In the figure, the angles `angleB` and `angleC` are the same.

Given that `angleC=40^@`
`=> angleB=angleC=40^@`
`=> angleA=180-(angleB+angleC)=180-(40+40)=100^@`
Given `angleA=2y+20`
`=> 2y+20=100^@`
`=> 2y=80^@`
`=> y=40^@`