高二 数学 数学 请详细解答,谢谢! (9 12:5:52)

1个回答

  • sin(3π-α)=√2cos(1.5π+β)

    sin[2π+(π-α)]=√2cos[π+(π/2)+β]

    sin(π-α)=-√2cos[(π/2)+β]

    -(-sinα)=-√2(-sinβ)

    sinα=√2sinβ

    √3cos(-α)=-√2cos(π+β)

    √3cosα=√2cosβ

    (sinα)²+(cosα)²=2(sinβ)²+(√6/3)²(cosβ)²

    =2(sinβ)²+2/3[1-(sinβ)²

    =4/3(sinβ)²+2/3

    =1

    (sinβ)²=1/4

    0<β<π

    sinβ=1/2

    β=π/6或5π/6

    sinα=√2sinβ=√2/2

    0<α<π

    α=π/4或3π/4

    故α=π/4,β=π/6或α=3π/4,β=5π/6