我是谶纬
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共回答了15个问题采纳率：100% 举报
cos(2arctan根号6+π/3)
=cos(2arctan根号6）cos(π/3)-sin(2arctan根号6)sin(π/3)
={2cos^2(arctan根号6)-1}*1/2-2sin(arctan根号6）cos（arctan根号6）*1/2*根号3
=cos^2(arctan根号6)-1/2-sin(arctan根号6）cos（arctan根号6）*根号3
又因为 cos(arctan根号6）= 1/根号7 sin(arctan根号6）=根号6/根号7
=1/7-1/2-3/7*根号2
=-5/14-3/7*根号2
1年前
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