角a满足sina=(k-3)/(K+5) cosa=(4-2k)/(k+5) 则tana=
问题描述：
角a满足sina=(k-3)/(K+5) cosa=(4-2k)/(k+5) 则tana=
答
tana=sina/ cosa
=[(k-3)/(K+5)] / [(4-2k)/(k+5)]
=k-3/4-2k
答
由恒等式sin²a+cos²a=1则[(k-3)²+(4-2k)²]/(k+5)²=15k²-22k+25=k²+10k+25k²-8k=0k=0,k=8所以tana=sina/cosa=(k-3)/(4-2k)=-3/4或-5/12