Which of the following cannot be the measures of an isosceles triangle ABC?

Options

A. Angle A is `50^(@)` and angle B is `80^(@)`
B. Angle A is `65^(@)` and angle B is `50^(@)`
C. Angle A is `60^(@)` and angle B is `70^(@)`
D. All of these

Answer

C

Explanation

If any two angles of a triangle are equal, then the triangle is isosceles.
The sum of all angles of a triangle is `180^(@)`.
Choice (a) : Angle A is `50^(@)` and angle B is `80^(@)`.
Angle C = `180^(@)-50^(@)-80^(@)=50^(@). rArrABC` is an isosceles triangle.
Choice (b) : Angle A is `65^(@)` and angle B is `50^(@)`.
Angle ` C= 180^(@)-65^(@)-50^(@)=65^(@).rArrABC` is an isosceles triangle.
Choice (c) Angle A is `60^(@)` and angle B is `70^(@)`.
Angle `C=180^(@)-60^(@)-70^(@)=50^(@)rArrABC` is not an isosceles triangle.
Hence, choice (c) follows.
Hence, the correct option is (c).