(sina+sinb)^2+(cosa+cosb)^2=?A.(COS(a-b)/2)^2B.4(COS(a-b)/2)^2C..(sin(a-b)/2)^2

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(sina+sinb)^2+(cosa+cosb)^2=?A.(COS(a-b)/2)^2B.4(COS(a-b)/2)^2C..(sin(a-b)/2)^2(sina+sinb)^2+(cosa+c

(sina+sinb)^2+(cosa+cosb)^2=?A.(COS(a-b)/2)^2B.4(COS(a-b)/2)^2C..(sin(a-b)/2)^2
(sina+sinb)^2+(cosa+cosb)^2=?
A.(COS(a-b)/2)^2
B.4(COS(a-b)/2)^2
C..(sin(a-b)/2)^2

(sina+sinb)^2+(cosa+cosb)^2=?A.(COS(a-b)/2)^2B.4(COS(a-b)/2)^2C..(sin(a-b)/2)^2
(sina+sinb)^2+(cosa+cosb)^2
=sin²a+2sina*sinb+sin²b+cos²a+2cosa*cosb+cos²b
=2+2(sina*sinb+cosa*cosb)
=2+2cos(a-b)

展开=1+1+2（sinasinb+cosacosb)=2+2cos(a-b)

sinA+sinB sinA-sinB cosA+cosB cosA-cosB sinA/sinB=cosB/cosA (sina-cosa)(sinb-cosb)化简 (cosa)^2(cosb)^2-(sina)^2(sinb)^2.为什么等于.(cosa)^2-(sinb)^2 求证:sina^2+sinb^2-sina^2*sinb^2+cosa^2*cosb^2=1 化简：sina^2+sinb^2-sina^2sinb^2+cosa^2cosb^2 (1+sina-cosa)/sina * (1+sinb-cosb) /sinb=2,求tana*tanba,b是锐角. 求证：cosa(cosa-cosb)+sina(sina-sinb)=2sin^2a-b/2 sina+2sinb,tana=3tanb,则cosa= 判断三角形形状：（SINA+SINB)(COSA+COSB)=2SINC 求证：sina+sinb/(cosa+cosb)=tan[(a+b)/2] 已知sina=2sinb.tana=3tanb,cosa sina+cosa=1/2,sinb-cosb=1/3 SinA=2SinB TanA=3TanB CosA=? 三角恒等公式cosa cosb sina cosb - cosa cosb cosa sinb - sina sinb sina cosb + sina sinb cosa sinb 约成最简在解释一下恒等公式sina + sinb 已知sinA+cosA=2sina,sinA*cosA=(sinb)^2,求证4(cos2a)^2=(cos2b)^2 已知sinA+cosA=2sina,sinA*cosA=(sinb)^2,求证4(sin2a)^2=(cos2b)^2 (sinA+cosA)的平方=2（sinB+1/sinB）,求A+B