请问SINA,SINB,SINC.COSA.COSB,COSC,TANA.TANB.TABC是指的哪个角,弄个简单的图象让我明白点吗?还有请问怎么才可以增加自己的积分,要不我没分赏你们了!~!~~!没什么 分,我刚注册的,麻烦了!~!

2sinc-sinb=sina cos c的最小值 SinA+SinB+SinC SinA+SinB+SinC sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2 已知cosA = cosθ×sinC,cosB = sinθ×sinc,求(sinA)^2+(sinB)^2+(sinC)^2的值 已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值 sinA+sinB+sinC=0; cosA+cosB+cosC=0,求cos(B-C)的值? 已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值 sina+sinb+sinc=0,cosa+cosb+cosc=0,求cos(B-C)的值? sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C) cos (A/2)=2sin[(C-B)/2],求证sinC-sinB=1/2sinA 11.在△ABC中,求证sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2) sinA,B,C之间转换的公式.比如sinA=sin(B+C),sinB= ,sinC= . 还有cos的 证明在△ABC中.sinA/(sinB+sinC)+sinB/（sinC+sinA）+sinC/(sinA+sinB)＜2证明 在三角形ABC中,已知sinAcos^2(C/2)+sinC-cos^2(A/2)=(3/2)sinB求证：sinA+sinC=2sinB 如何证明在三角形中sinA+sinB+sinC=4coc(A/2)*cos(B/2)*cos(C/2) 在△ABC中,若(sinA+sinC)(sinA-sinC)=sinB(sinA-sinB),则C= sinA+sinB=sinC(cosA+cosB),化简,