Given:
The angles of an isosceles triangle are,
∠M=40°
∠N=70°
The objective is to find the measure of ∠O.
An isosceles triangle is a triangle with two equal sides or two equal angles.
From the above figure, the two equal angles x are always larger than the third angle y.
Thus, the third angle will also be equal to the larger angle from the given agle.
Hence, the third angle is, ∠O = 70°.