(x+iy)is equal to [RPET 2001] - Vidyadip

MCQ

$\cos (x+iy)$is equal to [RPET 2001]

A
$\sin \,x\,\,\cosh \,y+i\,\cos \,x\,\,\sinh \,y$
B
$\cos \,x\,\,\cosh \,y+i\,\sin \,x\,\,\sinh \,y$
✓
$\cos \,x\,\,\cosh \,y-i\,\sin \,x\,\,\sinh \,y$
D
None of these

✓

Answer

Correct option: C.

$\cos \,x\,\,\cosh \,y-i\,\sin \,x\,\,\sinh \,y$

C

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