在平面直角坐标系xOy中,钝角α+[π/4]的顶点为坐标原点,始边与x轴的非负半轴重合.若α+[π/4]的终边与圆x2+

1个回答

  • (1)根据三角函数的定义,且α+[π/4]为钝角,得

    sin(α+[π/4])=t=[4/5],cos(α+[π/4])=-[3/5],

    2

    2(sinα+cosα)=[4/5],

    2

    2(cosα-sinα)=-[3/5],

    cosα=

    2

    10,sinα=

    7

    2

    10;

    (2)∵f(x)=cos([πx/2]+α),

    ∴f(1)=cos([π/2]+α)=-sinα=-

    7

    2

    10,

    f(2)