m (<C) = 45
m (<B) = 90
In a triangle the sum of angles = 180;
m (<A) = 180 - 90 - 45 = 45
sin A = sin 45 = [tex] \frac{ \sqrt{2} }{2} [/tex]
sin 45= cos 45 = [tex] \frac{ \sqrt{2} }{2} [/tex]
cos A = cos 45 = sin A
sin C = sin 45 = sin A
cos C = cos 45 = sin A
But tan C = tan 45 = 1
It means that the answer to you question is C) tan C