Q10 of 69 Page 9

The sum of two angles of a triangle is equal to its third angle. Determine the measure of the third angle.

Let,

∠1, ∠2 and ∠3 be the angles of a triangle.


∠1 + ∠2 = ∠3 (Given) (i)


We know that,


∠1 + ∠2 + ∠3 = 180o


∠3 + ∠3 = 180o [From (i)]


2∠3 = 180o


∠3 = 90o


Thus, third angle is 90o.


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