Find angle with given distance and height

[brycenrg]

Homework Statement

You have a device that shoots an object at an angle, on top of a desk.
You have x,y and v solve for the angle.
Origin is at the top of the desk.

Homework Equations

y=vyot+(½)ayt2
x = vxot
vsinΘ = vyo
vcosΘ = vxo

The Attempt at a Solution

y= vsinΘt + (1/2)at^2
x = vcosΘt → t = x/(vcosΘ)

y = x*(vsinΘ)/(vcosΘ) +(1/2)a(x/(vcosΘ))^2
y = xtanΘ + (a/2)*((x^2)/(v^2cos^2Θ))
from here i moved cos^2Θ to the left and changed tanΘ into sincos but I don't know how to isolate the Θ by itsself.

Does anyone have any ideas? I know quadratic equation can be used but i don't know how to change it for Θ

Any help is appreciated.[/B]

 

[Buzz Bloom]

Hi bryce:

Your title says you want the angle given the distance and height. Your problem statement does not mention a distance and height, ether as a number or as a variable. I suppose you might have in mind that x is distance and y is height, but then what has the desk got to do with it?

Regards,
Buzz

 

[TSny]

Try some trig identities: http://home.windstream.net/okrebs/page103.html