Question

In the diagram below, BELED, AC BC, and m/A = 71°. Find

m/D.
Step
1
try m/
Angle
m/A = 71°
B
71°
=
O
Reason.
Select a Reason
C
Given
E
D

Answer 1

Because AC = BC

=> ️ACB is a isosceles triangle at C

=> m<A = m<B = 71°

At triangle ABC

m<A + m<B + m<ACB = 180°

=> 71° + 71° + m<ACB = 180°

=> m<ACB = 38°

We have m<ACB and m<ECD are 2 opposite angle

=> m<ECD = m<ACB = 38°

At triangle ECD

m<ECD + m<E + m<D = 180°

=> 38° + 90° + m<D = 180°

=> m<D = 52°