Find the area of a rhombus with one diagonal twice as large as the other and with a side equal to 5.

By convention, this figure is a rhombus. Formula for finding the area of a rhombus through its diagonals:
S = 1/2 * d1 * d2;
Take d1 = x, then d2 = 2x
The diagonals in the rhombus are perpendicular, which means we can apply the Pythagorean theorem to find the diagonals. Let us find d1 using the Pythagorean theorem. 1/2 * d1 = 1/2 * x; 1/2 * d2 = x;
1 / 4x ^ 2 + x ^ 2 = 25
we get x = 2√5, which means d1 = 2√5, and d2 = 4√5;
S = 1/2 * d1 * d2;
Substitute the values and get:
S = 1/2 * 2√5 * 4√5;
S = 20;
answer: 20