一道英文数学题目(追加10分)

题目

一道英文数学题目(追加10分)
In priates of the caribbean, a cannon was fired at an enemy ship. The muzzle velocity was 60m/s. At what angle above the horizontal must the cannon have been aimed in order to hit the enemy ship 320 m away?(Dont worry about intial height on this one. The ships will be at the same level due to calm seas)
我用算式y=-4.9t^2+60sin(theta)t 和x=60 cos(theta)t 然后设320=60 cos(theta)t 然后我知道要用sin theta/cos theta 但是怎么做呢?

答案