∴在角α的终边上任取一点P(4t,-3t)(t≠0),
则x=4t,y=-3t,r=
x2+y2 |
(4t)2+(−3t)2 |
当t>0时,r=5t,
sinα=
y |
r |
−3t |
5t |
3 |
5 |
x |
r |
4t |
5t |
4 |
5 |
y |
x |
−3t |
4t |
3 |
4 |
当t<0时,r=-5t,sinα=
y |
r |
−3t |
−5t |
3 |
5 |
cosα=
x |
r |
4t |
−5t |
4 |
5 |
y |
x |
−3t |
4t |
3 |
4 |
综上可知,t>0时,sinα=−
3 |
5 |
4 |
5 |
3 |
4 |
t<0时,sinα=
3 |
5 |
4 |
5 |
3 |
4 |
x2+y2 |
(4t)2+(−3t)2 |
y |
r |
−3t |
5t |
3 |
5 |
x |
r |
4t |
5t |
4 |
5 |
y |
x |
−3t |
4t |
3 |
4 |
y |
r |
−3t |
−5t |
3 |
5 |
x |
r |
4t |
−5t |
4 |
5 |
y |
x |
−3t |
4t |
3 |
4 |
3 |
5 |
4 |
5 |
3 |
4 |
3 |
5 |
4 |
5 |
3 |
4 |