# Calc problem (dY/d? triangle)

1. Nov 19, 2005

### skivail

i don't understand how to figure this problem out, and i really need the help.

A kite is flying Y feet about the ground at the end of a 100 ft. string. the string makes an angle of ? (theta) with the ground.

1. find the equation for dY/d?. what are its units?

2. find dY/d? when Y= 50 feet. State the units

3. if the angular velocite d?/dT =.8 radians per second, how fast is the kite rising when Y=50 feet?

4. how fast is your answer to c in miles per hour?

I AM COMPLETELY LOST, EXCEPT FOR I AM PRETTY SURE I CAN FIGURE OUT NUMBER 4 ONCE I HAVE THE ANSWER TO NUMBER 3 SINCE THIS HAS NOTHING TO DO WITH CALCULUS. PLEASE HELP ME........

2. Nov 20, 2005

### skivail

oops, all of those ?'s are actually supposed to be thetas, but the computer messed it up when i posted. please help me.

3. Nov 20, 2005

### Pseudo Statistic

OK, use pythagoras theorem and draw a diagram..
100ft will be the hypotenuse (imagine it), Y is going to be, well, y... and using trigonometry you can express x in terms of the hypotenuse and theta...
Form the equation with y = blabla with theta somewhere and then differentiate with respect to theta...
For the question about what its units are, think of the derivative-- you're finding the rate of change of Y with respect to theta...... so given the unit of Y and the unit of theta, you can state the units as [unit of Y goes here] per [unit of theta goes here].
For 3, you're going to be using the chain rule; by the looks of it, you're finding dy/dT
4) Simple units conversion..

Hope I helped out some? Someone correct me if I'm wrong somewhere, please!