2010 National Question 2 Single-choice Differentiating 2010_quanguo_old_i 2.(5分)记$\cos(-80^\circ)=k$,那么$\tan100^\circ=$( ) A. $\frac{\sqrt{1-k^2}}{k}$B. $-\frac{\sqrt{1-k^2}}{k}$C. $\frac{k}{\sqrt{1-k^2}}$D. $-\frac{k}{\sqrt{1-k^2}}$ Answer keyB ☆ SaveCan't do it, show the explanation查看原卷 →