Question

Using \[\sin^2y+\cos^2y=1\] and \[\sin y=x\], what is \[\cos^2y\]?

Options

• \[\cos^2y=x\]

• \[\cos^2y=1+x^2\]

• \[\cos^2y=1-x^2\]

• \[\cos^2y=x^2-1\]

Answer 1

From \[\sin^2y+\cos^2y=1\], we get \[\cos^2y=1-\sin^2y\]. Substituting \[\sin y=x\] gives \[\cos^2y=1-x^2\].