Question

三角恒等变换1.已知tan(π/4+a)=1/2(1)求tan a的值(2)求(sin 2a-cos^2 a)/(1+c

Answer 1

1.(1)tan(π/4+a)=(tanπ/4+tana)/(1-tanπ/4*tana)=1/2

tana=-1/3

(2)原式=cosa(2sina-cosa)/2cosa^2=(2sina-cosa)cosa=2tana-1=-5/3

2.(1)设等于m

则sinx=1/10+m/2 cosx=1/10-m/2

(1/10+m/2)^2+(1/10-m/2)^2=1 m=-7/5(7/5不符合题意 舍)

（2）因为sinx=-3/5 cosx=4/5

带入得-24/175