Question

3) An exterior angle ofA ABC is 2 ACD. Prove that L A + B = LACD.​

Answer 1

Answer:

An exterior angle of a triangle is equal to the sum of the opposite interior angles.

Hence, In this case ∠A and ∠B

So,

∠A+∠B=140

as ∠A=∠B

or,2∠A=140

∠A=∠B=70

Answer 2

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In triangle ️ ABC

Using angle sum property of triangle.

/_ABC + /_ACB + /_CAB = 180°........(1)

Now, as BCD is a line.

So, /_ACB + /_ACD = 180°........(2)

Equate (1) and (2)

/_ABC + /_ACB + /_CAB = /_ACB + /_ACD

Therefore, /_ABC + /_CAB = /_ACD

Hence, proved.