# Area of a rectangle

Calculate the area of a rectangle with a diagonal of u = 12.5cm and a width of b = 3.5cm. Use the Pythagorean theorem.

Result

S =  42 cm2

#### Solution:

$u = 12.5 \ cm \ \\ b = 3.5 \ cm \ \\ \ \\ a^2 + b^2 = u^2 \ \\ \ \\ a = \sqrt{ u^2-b^2 } = \sqrt{ 12.5^2-3.5^2 } = 12 \ cm \ \\ \ \\ S = a \cdot \ b = 12 \cdot \ 3.5 = 42 = 42 \ cm^2$

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Pythagorean theorem is the base for the right triangle calculator. See also our trigonometric triangle calculator.

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