COSa=1/7,cos(a-b)=13/14,且0
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COSa=1/7,cos(a-b)=13/14,且0COSa=1/7,cos(a-b)=13/14,且0COSa=1/7,cos(a-b)=13/14,且0cos(a-b-a)=cosb=cos(a-
COSa=1/7,cos(a-b)=13/14,且0
COSa=1/7,cos(a-b)=13/14,且0
COSa=1/7,cos(a-b)=13/14,且0
cos(a-b-a)=cosb=cos(a-b)cosa+sin(a-b)sina
0
cosa=1/7,cos(a-b)=13/14且0
COSa=1/7,cos(a-b)=13/14,且0
三角函数 已知cosA=1/7 cos（A-B)=13/14 且0
已知cosa=1/7,cos(a-b)=13/14,0
19.已知cosa=1/7,cos(a-b)=13/14,0
已知cosa=1/7,cos(a-b )=13/14,且0
已知cosa=1/7,cos(a-b)=13/14,且0
已知cosA=1/7,cos(A-B)=13/14,且0
已知cosa=1/7,cos(a-b)=-13/14,且0
已知cosa=1/7,cos(a-b)=13/14且,0
cosA=1/7,cos(A+B)=13/14,o
cosa=1/7,cos(a+b)=-13/14,o
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