Câu 26. Cho $0^{\circ}<\alpha<90^{\circ}$. Khẳng định nào sau đây đúng?
A. $\tan \left(90^{\circ}-\alpha\right)=-\cot \alpha$.
B. $\sin \left(90^{\circ}-\alpha\right)=-\cos \alpha$.
C. $\cot \left(90^{\circ}-\alpha\right)=-\tan \alpha$.
D. $\cos \left(90^{\circ}-\alpha\right)=\sin \alpha$