Question

Given sinx=0.9 , what is cosx ?

Answer 1

The answer is cos x = 0.44

Answer 2

`\bf \textit{Pythagorean Identities} \\ \quad \\ sin^2(\theta)+cos^2(\theta)=1\implies cos^2(\theta)=1-sin^2(\theta) \\\\\\ cos(\theta)=\pm√(1-sin^2(\theta))\\\\ -----------------------------\\\\ thus \\\\\\ cos(x)=\pm √(1-(0.9)^2)`