作业帮sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?请问有何简便解法?
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sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?请问有何简便解法?
sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?
请问有何简便解法?
sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?请问有何简便解法?
sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)
=sin(x-20°)+sin(20°-x)+sin(x-20°)/cos(70°-x)
=sin(x-20°)-sin(x-20°)+sin(x-20°)/sin(x-20°)
=0+1
=1
按计算机，代两个数字进去，看看答案想不相同，相同的话，你运气太好了，干对了。
不一样，看看这个答案会和那些角的那个三角有关
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