2sina(x-π/4)sin(x+π/4) 怎么转换成(sinx-cosx)(sinx+cosx)?

2sina(x-π/4)sin(x+π/4) 怎么转换成(sinx-cosx)(sinx+cosx)? 1、f(x)=sin^2(x+π/4)-sin^2(x-π/4)的最小正周期是?2、已知sina=cos2a,π/2 sinA=x,sin(A/2)=? f(x)=(2cos^2 a/2-sina-1)/(sin(a+π/3)sin(a-π/3) 2sin(x+π/4)sin(x-π/4)=? sin^2(π/4 +x) 利用无穷小的性质计算下列极限lim sinx-sina/x-a(x→∞）还有一道：lim(1-x^2)/sinπx x→1 已知tan2a=3/4,f(x)=sin(a+x)+sin(a-x)-2sina的最小值为0 ,求sina+cosa的值 sin(x+π/4) 已知f（x）=4sin（3x+π/4）,若f（2/3a+π/12）=12/5,求sina的值 函数f(x)=-根号3sin²x+sinx×cosx,a属于(0,π),若f(a/2)=1/4-根号3/2,求sina的 求证:(sin 2x /(1-cos 2x) )·(sin x /(1+sin x))=tan (π/4-x/2). sina,sin(a+π/3)是方程f(x)=x^2-kx+k+5/4的两根,求ksina,sin(a+π/3)是方程x^2-kx+k+5/4=0的两根，求k 已知f(x)=√2sin(2x+π/4)+√2求F(x)=f(x)-f(x-π/4)的最大值,若F(a)=6/5,求sina. f(x)=（1+cotx)sin^2x-2sin(x+π/4)sin(x-π/4)还有一题, 已知函数f(x)=(1+1 anx)sin^2x+m sin(x+π/4)sin(x-π/4) cos(70+x)=4/5,(180＜x＜270),求sin(2x-40)、急求5道题…1、cos(70°+x)=4/5,(180°＜x＜270°),求sin(2x-40°)2、三角形ABC中,cosA*cosB＞sinA*sinB,判断三角形ABC的形状3、sin(x+π/3)+2sin(x-π/3)-√3cos(2/3π-x)4、tanα=log35^7,t limx→a -sin[(x+a)/2] =-sina为什么