Question

The range of a model rocket can be modelled by the equation R = 200cos20, where R is the range in meters and 0is the angle in radians above the horizontal that the rocket is launched. The target is 140 meters away. Determine the angle or angles that the rocket should be launched at to hit the target, to the nearest hundredth of a radian.

Answer 1

200 cos2θ = 140
cos2θ = 0.7
now finish it off

Answer 2

I have no idea what "cos" means.