simplify: cos(sin^-1(x/3))
\({\color{red}cos(arcsin \frac{x}{3})} \ or \ cos\frac{1}{\large sin\frac{x}{3}} \ ?\)
\(\large cos(arcsin \frac{x}{3})=cos(\frac{\pi}{2}-arccos\frac{x}{3})=cos \ arctan\frac{\frac{x}{3}}{\sqrt{1-\frac{x^2}{9}}}\)
Not easy, but great!
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