A=√sinx2 +9/16 B=√cosx2+1 倍角公式 a/sina=b/sinb sinb=√2/2 b=45
a2:b2=A2:B2 即 3cosx2+3=4sinx2+9/4 √1+cosx^2=2 1+cosx^2=4
7/2cos2X=3/2 arccos2x=7/3 cosx=√3
f(x)是什么呀 sinA=√2/2
f(x)=ab=1/2sin2x-1/4 4cos(2A+π/6)=sin
0< 2x< 2π/3 =2sin^2(π/6-A)-1
=Q
K=F(x)=Q+f(x)= -4