Simple differentiatian of tan question

[Dumbledore]

Homework Statement

What is the time rate of change of height after 5.0s?

Homework Equations

theta = 3t/(2t + 10)
adjacent length = 1000

Therefore: opposite length (height) h = 1000 tan (3t/(2t+10))

The Attempt at a Solution

I thought it would be simply finding the derivative of the second equation (dh/dt) and plugging in 5 for t.

dh/dt = 1000 * ( sec(3t/(2t+10)) )^2 * [ (2t+10)*3 - 3t(2)/ (2t + 10)^2 ]
dh/dt |t=5 = 1000/(cos.75)^2 * 3/40
= 75.01...

75 m/s

Is this not correct?

 

[Dick]

Change your calculator from degrees to radians. Otherwise, it looks great.

 

[Dumbledore]

Thank you.