I have limited time please help

An arrow is shot vertically upward at a rate of 180ft/s. use the projectile formula h=−16t2+v0t to determine at what time(s), in seconds, the arrow is at a height of 420ft. round your answer(s) to the nearest tenth of a second.

Cos^2x+cos^2(120°+x)+cos^2(120°-x)i need this asap. pls me

Me i'm timed right now! a. (0,-5)b. (0,-3)c. (0,3) d. (0,5)