\(f(x) = cos(x)\)
\(f(\frac{\pi}{2}) = cos(\frac{\pi}{2})\)
\(f(90) = cos(90)\)
\(f(90) = 0\)
\(f'(x) = -sin(x)\)
\(f'(90) = -sin(90)\)
\(f'(90) = -1\)
\(L(x) = f(90) + f'(90)(x - 90)\)
\(L(x) = 0 - 1(x - 90)\)
\(L(x) = -1(x) + 1(90)\)
\(L(x) = -x + 90\)
\(L(x) = -x + \frac{\pi}{2}\)
