We only know 1 side, and that is the width of 4. We only have the diagonals at our side. Half of the diagonal is 5. As a result, the diagonal is 10. I want you to imagine a triangle that has a base of 4 and a hypotenuse of 10. Use the Pythagorean Theorem to find b, or the height.
a² + b² = c²
4² + b² = 10²
16 + b² = 100
100 - 16 = 84
b² = 84
b = √84
b ≈ 9.165
Now we know the length of the rectangle, which is about 9.165. Multiply that by 4 to get the area.
9.165 * 4
36 + 0.4 + 0.24 + 0.020
36.4 + 0.24 + 0.02
36.64 + 0.02
36.66u²
The area of rectangleRSTU is about 36.66units squared.
