97台南縣國中

[ruby0519]

7.設f(x)=4x^3+2x^2-3x-1,試求f(cos75)=?

[thepiano]

f(x) = (4x^3 - 3x) + (2x^2 - 1)
f(cosθ) = cos3θ + cos2θ
......