已知函数fx=2sin(1/3x-π/6),x∈R1.求f(5π/4)的值2.设α,β∈[0,π/2],f(3α+π/2)=10/13,f(3β+2π)=6/5,求cos(α+β)的值

Question

已知函数fx=2sin(1/3x-π/6),x∈R
1.求f(5π/4)的值
2.设α,β∈[0,π/2],f(3α+π/2)=10/13,f(3β+2π)=6/5,求cos(α+β)的值

Answer 1

已知函数fx=2sin(1/3x-π/6),x∈R1.f(5π/4)=2sin(1/3x5π/4-π/6)=2sinπ/4=√22.设α,β∈[0,π/2],f(3α+π/2)=10/13,f(3β+2π)=6/5,求cos(α+β)的值f(3α+π/2)=2sina=10/13∴sina=5/13,cosa=12/13f(3β+2π)=...