sinx |
1+cosx |
y′=
(sinx)′(1+cosx)−sinx(1+cosx)′ |
(1+cosx)2 |
=
cosx+cos2x+sin2x |
(1+cosx)2 |
=
1+cosx |
(1+cosx)2 |
1 |
1+cosx |
所以cosx=−
1 |
2 |
2 |
3 |
故选B.
sinx |
1+cosx |
π |
3 |
2 |
3 |
π |
4 |
π |
6 |
sinx |
1+cosx |
(sinx)′(1+cosx)−sinx(1+cosx)′ |
(1+cosx)2 |
cosx+cos2x+sin2x |
(1+cosx)2 |
1+cosx |
(1+cosx)2 |
1 |
1+cosx |
1 |
2 |
2 |
3 |