In a ΔABC, if AB = AC and BC is produced to D such that ∠ACD = 100°, then ∠A =

(a) 20°

(b) 40°

(c) 60°

(d) 80°

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Solution

In the triangle ABC it is given that

We have to find

Now (linear pair)

Since

So, (by isosceles triangle)

This implies that

Now,

(Property of triangle)

Hence (a).

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