help!

[dahlia]

hello, i need help on this question.

A plane flying with a constant speed of 25km/min passes over a ground radar station at an altitude of 15km and climbs at an angle of 20 degrees. At what rate, in km/min is the distance from the plane to the radar station increasing 3 minutes later?

Since it is climbing at an angle of 20 degrees, i can't simply use pythagorean theorem and take y prime..
can anyone give me an advice how to approach to this question?

 

[Gene]

The plane is at height y=15+25*sin(20)*t
It is at horizontal distance x=25*cos(20)*t
Total distance s = sqrt(x²+y²)
Find ds/dt at t=3