7. In Rt $\triangle A B C$, $\angle C=90^{\circ}$. Which of the following equations is not necessarily true? ( ).
(A) $\sin A=\sin B$
(B) $\cos A=\sin B$
(C) $\sin A=\cos B$
(D) $\sin (A+B)=\sin C$
7.A. When $\angle A \neq \angle B$, $\sin A \neq \sin B$.