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Homework Statement
A projectile is launched from O with speed u at angle theta to the horizontal. In its subsequent trajectory it just clears two obstacles of height h at horizontal distances d and 2d from O, respectively.
http://img403.imageshack.us/img403/4369/projectile.jpg
Show that tan (theta) = 3h/2d
Homework Equations
The Attempt at a Solution
I do not see anyway to get tan (theta) here. From class I have the following equations:
Solution of the equation of motion:
r(t)=(utcos(theta))i + (utsin(theta) - ½gt²)j
trajectory is parabola with equation:
y=xtan(theta)-x²(g/2u²)(1+tan²(theta))
but I cannot see how I begin to find just tan(theta)
I just need to know where to start. My guess is I'm missing something that's taken to be 'obvious' but what my professor thinks is 'obvious' is usually obscure for me :)
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