Use a Double Angle Formula to Rewrite the Given Expression $$10 \cos ^ { 2 } x - 5$$

Multiple Choice

Use a double angle formula to rewrite the given expression. $$10 \cos ^ { 2 } x - 5$$

A) $5 \cos 5 x$
B) $5 \cos 2 x$ ​
C) $10 \cos 2 x$ ​
D) $2 \cos 10 x$ ​
E) $2 \cos 5 x$ ​