Fundamental Identity

Geometry Level 2

If sin ⁡ x = 3 5 \sin x = \frac{3}{5} and 0 < x < π 2 0<x<\frac{\pi}{2} , find cos ⁡ x \cos x

2 5 \frac{2}{5} 16 25 \frac{16}{25} 4 5 \frac{4}{5} 9 25 \frac{9}{25}

Victor Paes Plinio by Victor Paes Plinio , 21, Brazil

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1 solution

Ahmad Saad
Jul 29, 2017

cosx = sqrt[1 - sin^2 x] = sqrt[1 - 9/25] = sqrt[16/25] = 4/5 such that 0< x <pi/2

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