In the given figure AD = AB = AC BD is parallel to CA a

In the given figure AD = AB = AC BD is parallel to CA a
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In the given figure, AD = AB = AC, BD is parallel to CA and angle ACB = 65°. The measure of DAC is

A. 50

B. 80

C. 130

D. 150

Please scroll down to see the correct answer and solution guide.

Right Answer is: C

SOLUTION

We can see that ABC is an isoceles triangle with side AB = side AC.
ACB=ABC  (In a triangle, if two sides are equal, then the angles opposite to these sides are also equal).
As ACB=65, we must have ABC=65
We know that, the sum of all the angles of a triangle is 180.
ACB+CAB+ABC=180
65+65+CAB=180
CAB = 180130
i.e., CAB=50

As BD is parallel to CA, we must have, CAB=DBA, since they are alternate angles.
CAB=DBA=50

We see that ADB is an isosceles triangle with Side AD = Side AB.
ADB=DBA=50
Since sum of all the angles of a triangle is 180°,
ADB+DAB+DBA=180°
50+DAB+50=180
DAB=180100=80
DAB=80

The angle DAC is sum of angle DAB and CAB.
DAC=CAB+DAB
DAC=50+80
i.e., DAC=130