Question

In a triangle ABC, AB = AC and BC is produced to D angle ACD = 100. Then angle A ?​

Answer 1

Step-by-step explanation:

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

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Answer 2

Answer:

ANGLE A = 20 degrees

Step-by-step explanation:

In Triangle ABC

AB=AC (given)

Then Angle ABC = Angle ACB ( Angles opposite to equal sides are equal or it is an isoceles triangle )

Now, Angle ACB and angle ACD forms linear pair

Angle ACB+ Angle ACD = 180

Angle ACB + 100 = 180

Angle ACB = 80 degrees = Angle ABC

Now in triangle ABC , BY angle sum property

Angle ABC + Angle ACB + Angle BAC = 180

80 + 80 + Angle BAC = 180

160 degree + angle BAC = 180

Angle BAC = 180 - 160

Angle BAC = Angle A = 20 degrees