# 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:

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

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