【证明】Sin A+sin B=2Sin 22
【证明】Sin A+sin B=2Sin 22
证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b,
证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b, 并利用该式计算sin^2 20度=sin 80度
证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2)
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2
证明sin(a+b)=sinacosb+cosasinb
三角形ABC中证明 COSA+COSB+COSC=1+4SIN(A/2)*SIN(B/2)*SIN(C/2)
证明sin(a+b)sin(a-b)=sin²a-sin² b,并用该式计算sin²20°
cos(a+b)=cos(a)*cos(b)-sin(a)*sin(b) 用三角形证明
已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围
此式求证明sin(a+b)sin(a-b)=sin2a-sin2b 2代表的是平方