1. Nov 20, 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(theta). what are its units?
2. find dY/d(theta) when Y= 50 feet. State the units
3. if the angular velocite d(theta)/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........THIS IS A REVIEW PROBLEM FOR A TEST I HAVE ON MONDAY (TWO DAYS FROM NOW), AND IF I CAN'T FIGURE OUT HOW TO DUE THESE TYPE OF PROBLEMS, I AM IN BIG TROUBLE......

2. Nov 20, 2005

### ms. confused

This one's tough. Have you drawn it out for yourself? If you did, you know you'd have some sort of trig relationship relating the hypotenuse the opposite side and angle theta. I'm wondering, since they gave you Y but not theta, if you should use arcsine (inverse trig relation) to find theta.

arcsinx = Y/100
100arcsinx= Y
100/sqrt(1-x^2x') = YY'
.
.
.
Only problem is you end up with two unknowns using this method...oops. Y' would be the ideal thing to find on #3 but for that you need x (theta), which I am now stumped on how to find. Units for 1 and 2 would probably be feet per radian...

3. Nov 20, 2005

### Tide

Why don't you just write $y = 100 \sin \theta$ and differentiate?