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