Question

$\cos(i^{5}x)$ equals.

• A. $i\cosh x$
• B. $- i\cosh x$
• C. $\cosh x$
• D. $- {\cos h}x$

Answer 1

Answer: (C)

$\cosh x$

Answer 2

$\cos(i^{5}x) = \cos(ix) = {\cos h}x$.