| sin x | ||
f(x) = | ||
| cos 2x |
| cos x* cos 2x − sin x*( − 2 sin 2x) | ||
f '(x) = | = | |
| cos2 2x |
| cos x*cos 2x + 2sin x*sin 2 x | ||
= | ||
| cos2 2x |
| π | 0*(−1)+ 2*1*0 | |||
f '( | ) = | = 0 | ||
| 2 | (−1)2 |
| sin x | ||
f(x) = | ||
| cos 2x |
| cos x* cos 2x − sin x*( − 2 sin 2x) | ||
f '(x) = | = | |
| cos2 2x |
| cos x*cos 2x + 2sin x*sin 2 x | ||
= | ||
| cos2 2x |
| π | 0*(−1)+ 2*1*0 | |||
f '( | ) = | = 0 | ||
| 2 | (−1)2 |