sin(a+π/3)+sina= - 4根号3/5,则cos(a+2π/3)怎么求》

sinA=3sin(2π/3-A) SINA=?sinA=3sin(2π/3-A) SINA=?答案是-3√3cosA sin(a+kπ)=2cos[a+(k+1)π].求5cosa+3sina/4sina-2cosa sin(a+kπ)=2cos[a+(k+1)π].求5cosa+3sina/4sina-2cosa 已知tan{π/4+a}=3,求sina*sin(3π /2 +a)-sin^2a+1的值 sin(6/π-a)=1/3 sina= 已知sin(π+a)=1/3,则sina= 为啥sina+cosa=√2sin(a+π/4) sin(3π-a)=sina?三角函数诱导 1- sin(2π/3 - a)/sina sin(a-pia/4)=3/5,求sina 已知sina=1/3,则sin(a+π/4)cos(a+π/4) 设(sina)^2-sina-2(cosa)^2=0,求sin(a-3π/2) 已知tan(π-a)=2,求值：（1）2sin+2cosa/7sina+cosa（2）sina*cosa（3）4cosa^2+3sina^2 假如令θ=a,则sin(3π+θ)=-sinθ=-sina=1/4,sina=-1/4,为什么的? 化简sin(π/4+a)cosa-sin(π/4-a)sina= sin(4分之π+a)sin(4分之π-a) sina=二分之一 证明sinA+sin(A+2π/3)+sin(A-2π/3)=0 证明sinA+sin(A+2π/3)+sin(A-2π/3)=0