Area of a rectangle

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

Correct answer:

S =  42 cm²

Step-by-step explanation:

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

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