Question

in triangle ABC exterior angle at b=150° and interior angle c=70° then find interior angle A​

Answer 1

Step-by-step explanation:

Theorem: An measure of an exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles.

So In our case ∠CAB and ∠CBA are the two non-adjacent interior angles corresponding to the exterior angle.∠DCA. and

∠ACB and ∠BAC are the two non-adjacent interior angles corresponding to the exterior angle.∠ABE.

Hence, ∠CAB+∠CBA=∠DCA..........(1)

And,

∠CAB+∠BCA=∠ABE..........(2)

Adding (1) and (2) we get,

∠ABE+∠DCA=180°+∠BAC

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