f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θf(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/13 06:17:47
![f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θf(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ](/uploads/image/z/11727542-38-2.jpg?t=f%28x%29%3D3%2F2%E6%A0%B9%E5%8F%B73sinx%2Acosx%2Bcos%5E2%28x-%CF%80%2F6%29-3%2F2sin%5E2x%2B1%2F4+%E8%8B%A5f%28X%29%3D4%2F5%280%EF%BC%9C%CE%B8%EF%BC%9C%CF%80%2F2%29%E6%B1%82sin2%CE%B8%26%238203%3Bf%28x%29%3D3%2F2%E6%A0%B9%E5%8F%B73sinx%2Acosx%2Bcos%5E2%28x-%CF%80%2F6%29-3%2F2sin%5E2x%2B1%2F4+%E8%8B%A5f%28X%29%3D4%2F5%280%EF%BC%9C%CE%B8%EF%BC%9C%CF%80%2F2%29%E6%B1%82sin2%CE%B8)
f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θf(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ
f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ
f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ
f(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θf(x)=3/2根号3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4 若f(X)=4/5(0<θ<π/2)求sin2θ
f(x)=3/2√3sinx*cosx+cos^2(x-π/6)-3/2sin^2x+1/4
=3√3/4sin2x+1/2(1+cos(2x-π/3)-3/4(1-cos2x)+1/4
=3√3/4sin2x+1/2cos(2x-π/3)+3/4cos2x
=3√3/4sin2x+1/4cos2x+√3/4sin2x+3/4cos2x
=√3sin2x+cos2x
=2(√3/2sin2x+1/2cos2x)
=2sin(2x+π/6)
f(θ)=2sin(2θ+π/6)=4/5
sin(2θ+π/6)=2/5
0<θ<π/2,π/6<2θ+π/6<7π/6
cos(2θ+π/6)=√21/5或cos(2θ+π/6)=-√21/5
sin2θ=sin[(2θ+π/6)-π/6]=√3/2sin(2θ+π/6)-1/2cos(2θ+π/6)
=√3/2*2/5-1/2*√21/5=(2√3-√21)/10或
sin2θ=√3/2*2/5+1/2*√21/5=(2√3+√21)/10
即sin2θ=(2√3-√21)/10或sin2θ=(2√3+√21)/10