已知角α终边上一点P(-4,3),求cos(π2+α)−sin(−π−α)cos(11π2−α)+sin(9π2+α)的值.

问题描述:

已知角α终边上一点P(-4,3),求

cos(
π
2
+α)−sin(−π−α)
cos(
11π
2
−α)+sin(
2
+α)
的值.

∵角α终边上一点P(-4,3),
∴tanα=

y
x
=-
3
4

则原式=
−sinα−sinα
−sinα+cosα
=
−2tanα
−tanα+1
=
−2×(−
3
4
)
3
4
+1
=
6
7