Because we know an isosceles right triangle's angles to be 45°, 45°, and 90°, we can work out the equal side lengths a with trigonometry.
Calculate the cosine of 45° as:
cos(45°) = 1 / √2 = 0.7071
As the cosine represents the ratio of the adjacent side a to the hypotenuse b, we can say that:
cos(45°) = a / b
Make a the subject and complete the equation:
a = b × cos(45°) = 14.14 cm
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