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】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)=sin²a-sin² b,并用该式计算sin²20°
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2)
证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2
已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围
sin^2A+sin^2B=sin^2C求证△ABC的形状
在三角形ABC中,sin*2A+sin*2B=sin*2C
在三角形ABC中sin^A+sin^B=2sin^C,则角C为?
三角形ABC中证明 COSA+COSB+COSC=1+4SIN(A/2)*SIN(B/2)*SIN(C/2)