Question

(1) Some isosceles triangles are drawn below. In each, one angle is given
Find the other angles.
40°
30°​

Answer 1

in the first triangle where the given side is 40°

as the following triangle is an isosceles triangle so the two sides must be equal.so two sides will have 40° angle.

let the other angle be X°

we know that ,

the interior angle of a triangle = 180°

or,40°+40°+x°=180°

or,80°+x°=180°

or,x°=180°-80°

or,x°=100°

in the second triangle where the given side is 30°

as the following triangle is an isosceles triangle so the two sides must be equal.so two sides will have 30° angle.

let the other angle be X°

we know that,

the interior angle of a triangle = 180°

or,30°+30°+x°=180°

or,60°+x°=180°

or,x°=180°-60°

or,x°=120°