This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
Since the triangle is isosceles, the other two sides have equal length. Call the length of each side x.

Draw a perpendicular from vertex to the base and recall that this is also a bisector of base. Therefore you get a right triangle with a leg 20 and one angle 70^{\circ}. The other side can be obtained by applying cosine ratio :
\cos(70^{\circ})~=~\frac{20}{x}\implies x = \frac{20}{\cos(70^{\circ})}~\approx~58.48

Add up the sides to get the perimeter
1 5 1
can you answer my another question again ?