Question

Rectangle ABCD and equilateral triangle ECD are on the same base DC. if DC=10cm. Then find the area of rectangle ABCD.

Answer 1

Area of equilateral ΔECD= area of rectangle ABCD (same base and vertical height of the triangle is twice that of the rectangle)
So,
Area of the equilateral triangle = √3/4 × s²  
= √3/4 ×10²
= 1.732 x 100/4
= 173.2/4
= 43.3 sq cm

Answer 2

Step-by-step explanation:

Area of equilateral triangle ECD equals to that of the rectangle ABCD because they have the same base DC and the vertical height of the triangle is twice that of the rectangle.

So,

Area of the equilateral triangle = √3/4 × s²  where s = each side of the equilateral triangle.

= √3/4 ×10²

= 1.732*100/4

= 173.2/4

Area of the equilateral triangle = 43.3 sq cm