# The side of the rectangle is 15 cm, and its diagonal is 17 cm. Find the area of the rectangle.

September 30, 2021 | education

| From the condition, we know that the side of the rectangle is 15 cm, and its diagonal is 17 cm.In order to find the area of the rectangle, we apply the following formula:

S = a * b;

We know the length of one of the sides and we need to find the length of the second. Let’s apply the Pythagorean theorem for this.

The diagonal and the two sides of the rectangle form a right-angled triangle. We are looking for an unknown leg:

c ^ 2 = a ^ 2 – b ^ 2;

a = √ (c ^ 2 – b ^ 2) = √ (17 ^ 2 – 15 ^ 2) = √ (289 – 225) = √64 = 8 cm length of the second side of the rectangle.

S = 15 * 8 = 120 cm ^ 2.

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