Evaluate cos(arcsin(x))

$\cos (\arcsin (x))$

Step 1

Write the expression using exponents.

Draw a triangle in the plane with vertices $(\sqrt{1^{2} - x^{2}}, x)$ , $(\sqrt{1^{2} - x^{2}}, 0)$ , and the origin. Then $\arcsin (x)$ is the angle between the positive x-axis and the ray beginning at the origin and passing through $(\sqrt{1^{2} - x^{2}}, x)$ . Therefore, $\cos (\arcsin (x))$ is $\sqrt{1 - x^{2}}$ .

$\sqrt{1 - x^{2}}$

Rewrite $1$ as $1^{2}$ .

$\sqrt{1^{2} - x^{2}}$

Step 2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = 1$ and $b = x$ .

$\sqrt{(1 + x) (1 - x)}$

Evaluate cos(arcsin(x))

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