Cos x=1/4, find cos2x if x is in the first quadrant

Pls answer ASAP

The volume of a cube is 8 in to the 3rd power. how long is each side?

The swimming pool is open when the high temperature is higher than 20∘c. lainey tried to swim on monday and thursday (which was 3 days later). the pool was open on monday, but it was closed on thursday. the high temperature was 30∘c on monday, but decreased at a constant rate in the next 3 days. write an inequality to determine the rate of temperature decrease in degrees celsius per day, d, from monday to thursday.

I’m stuck on this equation, anyone got the answer?