sinA+sinC为什么等于sin(A+C)/2cos(A-C)/2
在三角形ABC中.已知sin^2A+sin^2B*sin^2C=sinB*sinC+sinC*sinA+sinA*sin
cos^2A - cos^2B + sin^2C=2cosA *sinB *sinC证明
cos^2A - cos^2B + sin^2C=2cosA *sinB *sinC
在△ABC中,求证:sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2)
11.在△ABC中,求证sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2)
在△ABC中,三个内角∠A、∠B、∠C满足sin^2A+sin^2C-sinA*sinC=sin^2B,则角B=
已知三角形ABC中,sinA,sinB ,sinC是等差数列,求证2cos(A+C)/2=cos(A-C)/2
sinA+sin(150°-A)为什么等于2sin75°cos(75°-A)
sina+sinb+sinc=0 cosa+cosb+cosc=0求证cos*2a+cos*2b+cos*2c=3|2
在三角形ABC中求证sinA+sinB+sinC=4cos(A/2)COS(B/2)COS(C/2)证到这步然后怎么证:
不等式题目:在△ABC中请证明sinA+sinB+sinC≤cos(A/2)+cos(B/2)+cos(C/2)
在三角形ABC中,求证:sin^A/2+sin^B/2+sin^C/2=1-2sinA/2sinB/2sinC/2