cos(-B)=cosB sin(-B)=-sinB为什么是这样,不懂根据哪些公式可以得出此公式?
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sin²a+sin²b-sina²sin²b+cos²cosb=1
cosb=cos[(a+b)-a]=cos(a+b)cosa+sin(a+b)sina
cos(a-b)cosb-sin(a-b)sinb等于什么
化简cos(a+b)cosb+sin(a+b)sinb
cos(a-b)cosb-sin(a-b)sinb
化简:cos(A-B)cosB-sin(A-B)sinB
cos a+cosb=-1/3 sin a+sin b=1/2 求cos(a+b)
[sin(2a+b)cosb+cos(2a+b)sinb]/[cos(2a+b)cosb]=[sin(2a+2b)]/[cos(2a+b)cosb]是怎么来的,看不懂
为什么sinb=sin(a+b-b)=sin(a+b)cosb+cos(a+b)sinb,这是公式吗?
(sinB-cosB)^2/sin^2B-cos^2B=3,那么,tanB等于什么
sin(a+b)cos(a-b)=sina*cosa+sinb*cosb
求证:sin(a+b)cos(a-b)=sina*cosa+sinb*cosb麻烦个位 帮个忙~
sinA(cos(2A+B)+cosB)=cosA(sin(2A+B)-sinB)证明
证明下列恒等式:sin(a+b)*cos(a-b)=sina*cosa+sinb*cosb
cos(A+B)+sin(A-B)=(cosA+sinA)(cosB-sinB)
cos(A-B)-sin(A+B)=(cosA-sinA)(cosB-sinB).
sin(a-b)cosb+cos(b-a)sinb=cos(b-a)怎么变形,为什么?
证明cosA+cosB+cosC=1+4sin(A/2)sin(B/2)sin(C/2)证明:cosA+cosB+cosC=1+4sin(A/2)sin(B/2)sin(C/2)尽量详细一点选做cosA+cosB+cosC=1+4sin(A/2)sin(B/2)sin(C/2) cos(180-B-C)+cosB+cosC=1+2sin(A/2)[2sin(B/2)sin(C/2)] cos(180-B-C)+cosB+cosC