Trong các khẳng định sau, khẳng định nào sai sinx = sin alpha

A. $\sin x=\sin a\iff \left[\begin{array}{c}x=\alpha +k2\mathrm{\pi }\\ x=\mathrm{\pi }-\mathrm{\alpha }+\mathrm{k}2\mathrm{\pi }\end{array}\right.\left(k\in Z\right)$

B. $cosx=cosa\iff \left[\begin{array}{c}x=\alpha +k2\mathrm{\pi }\\ x=\mathrm{\pi }-\mathrm{\alpha }+\mathrm{k}2\mathrm{\pi }\end{array}\right.\left(k\in Z\right)$

C. $\tan x=\tan a\iff x=\alpha +k2\mathrm{\pi } \left(k\in Z\right)$

D. $cosx=cosa\iff \left[\begin{array}{c}x=\alpha +k2\mathrm{\pi }\\ x=-\mathrm{\alpha }+\mathrm{k}2\mathrm{\pi }\end{array}\right.\left(k\in Z\right)$