化简计算cos(80°+3α)cos(35°+α)+sin(80°+α)cos(55°-α)的过程?
题目
化简计算cos(80°+3α)cos(35°+α)+sin(80°+α)cos(55°-α)的过程?
没有打错,是3α
^.^
答案
cos(80°+α)cos(35°+α)+sin(80°+α)cos(55°-α)
=cos(80°+α)cos(35°+α)+sin(80°+α)sin(35°+α)
=cos[(80°+α)-(35°+α)]
=cos55°
cos(80°+3α)?
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