Question 13 Marks
If one angle of an isosceles triangle is 70°, then find the possibilities for the other two angles
Answer
View full question & answer→(i) Given one angle $=70^{\circ}$
Also, it is an isosceles triangle
Another angle also can be $70^{\circ}$
Sum of these two angles $=70^{\circ}+70^{\circ}=140^{\circ}$
We know that the sum of three angles in a triangle $=180^{\circ}$
Third angle $=180^{\circ}-140^{\circ}=40^{\circ}$
One possibility is $70^{\circ}, 70^{\circ}$ and $40^{\circ}$
(ii) Also if one angle is $70^{\circ}$
Sum of other two angles $=180^{\circ}-70^{\circ}=110^{\circ}$
Both are equal
They are $\frac{110}{2}=55^{\circ}$
Another possibility is $70^{\circ}, 55^{\circ}$ and $55^{\circ}$.
Also, it is an isosceles triangle
Another angle also can be $70^{\circ}$
Sum of these two angles $=70^{\circ}+70^{\circ}=140^{\circ}$
We know that the sum of three angles in a triangle $=180^{\circ}$
Third angle $=180^{\circ}-140^{\circ}=40^{\circ}$
One possibility is $70^{\circ}, 70^{\circ}$ and $40^{\circ}$
(ii) Also if one angle is $70^{\circ}$
Sum of other two angles $=180^{\circ}-70^{\circ}=110^{\circ}$
Both are equal
They are $\frac{110}{2}=55^{\circ}$
Another possibility is $70^{\circ}, 55^{\circ}$ and $55^{\circ}$.
