Question

In fig, AB=AC and angle ACD=120 degree.find angleA

Answer 1

Answer:

angle ABC=angleACB

angleACB=180-120

angleACB=60

angleABC=60

angleA = 60

Answer 2

Question:

In fig.,AB=AC and ∠ACD=120°.Find ∠A.

Answer:

We have,

AB=AC

➙∠B=∠C. [∵Angles opposite to equal sides are equal]

Now,∠ACB+∠ACD=180°. [Angles of a linear pair]

➙ ∠C+120°=180°

➙ ∠C=60°

➙ ∠B=60°. [∵∠B=∠C]

Using angle sum property in ∆ABC,we obtain

∠A+∠B+∠C=180°

➙ ∠A+60°+60°=180°. [∠B=∠C=60°]

➙ ∠A=60°