Question

In a triangle ABC if AC=BC is produced to D such that angle ACD=100° then angle A =?

Answer 1

Answer:

angle A is 100 degree because angle congruent to congruent side.

Answer 2

Given:

In triangle ABC

AB=AC

Angle ACD=100 degree

To find:

Angle A

Solution:

AB=AC

Angle ABC=Angle ACB

Reason:Angle made by equal sides are equal

Angle ACD=100 degree

Angle ACB+angle ACD=180 degree

Reason: Linear pair sum

Angle ACB=180-100=80 degrees

Angle ABC=80 degrees

Angle A+Angle ABC=Angle ACD=100 degrees

Reason: Exterior angle is equal to sum of interior opposite angles .

Angle A=100-angle ABC=100-80=20 degree

Hence, the angle A=20 degree