Question

In an isosceles triangle, one angle is 70°. The other two angles are of

(i) 55° and 55° (ii) 70° and 40° (iii) any measure

In the given option(s) which of the above statement(s) are true?

(a) (i) only (b) (ii) only (c) (iii) only (d) (i) and(ii)

Answer 1

(d) (i) and (ii)

From the question it is given that,

One angle of isosceles triangle is 70^o.

We know that, in an isosceles triangle 2 angles are equal corresponding with 2 equal sides,

If 70^o is 3^rd angle of triangle,

70^o + x + x = 180^o

2x + 70^o = 180^o

2x = 180^o – 70^o

x = (110^o/2)

x = 55^o

So, both angles are 55^o

Consider the 70^o as base angle of isosceles triangle

Then, 70^o + 70^o + x = 180^o

x = 180^o – 140^o

x = 40^o

So, one angle is 40^o and another is 70^o