# Find Angle Theta

• Jan 7th 2009, 03:18 PM
magentarita
Find Angle Theta
A 10-meter telephone pole casts a shadow directly down a slope when the angle of elevation of the sun is 42 degrees.
Find theta, the angle of elevation of the ground.

• Jan 8th 2009, 12:25 AM
Prove It
Quote:

Originally Posted by magentarita
A 10-meter telephone pole casts a shadow directly down a slope when the angle of elevation of the sun is 42 degrees.
Find theta, the angle of elevation of the ground.

Remember that the sum of three angles in a triangle is $180^{\circ}$.

Provided that the telephone pole is perpendicular to the ground (as all are), then $90^{\circ} + 42^{\circ} + \theta ^{\circ} = 180^{\circ}$.

$132^{\circ} + \theta ^{\circ} = 180^{\circ}$

$\theta ^{\circ} = 48^{\circ}$.
• Jan 9th 2009, 09:06 AM
magentarita
but...
Quote:

Originally Posted by Prove It
Remember that the sum of three angles in a triangle is $180^{\circ}$.

Provided that the telephone pole is perpendicular to the ground (as all are), then $90^{\circ} + 42^{\circ} + \theta ^{\circ} = 180^{\circ}$.

$132^{\circ} + \theta ^{\circ} = 180^{\circ}$

$\theta ^{\circ} = 48^{\circ}$.

But this is trigonometry not geometry, right? I was told that we must take the inverse if the trig function to find theta.
• Jan 9th 2009, 12:48 PM
Math Major
Quote:

Remember that the sum of three angles in a triangle is http://www.mathhelpforum.com/math-he...a552d7be-1.gif.

Provided that the telephone pole is perpendicular to the ground (as all are), then http://www.mathhelpforum.com/math-he...2a964305-1.gif.

http://www.mathhelpforum.com/math-he...c26aa60e-1.gif

http://www.mathhelpforum.com/math-he...a0de8356-1.gif.
I believe the mistaken assumption was that the angle of elevation was angle between the top of the telephone poll and the shadow being cast. The angle of elevation for the sun is going to be the angle between the ground and the sun. Further, the telephone poll appears to be casting a shadow down a hill, not across a plane. The question is asking for the angle of elevation for the hill.
• Jan 9th 2009, 01:21 PM
masters
Quote:

Originally Posted by Math Major
I believe the mistaken assumption was that the angle of elevation was angle between the top of the telephone poll and the shadow being cast. The angle of elevation for the sun is going to be the angle between the ground and the sun. Further, the telephone poll appears to be casting a shadow down a hill, not across a plane. The question is asking for the angle of elevation for the hill.

A diagram would be nice. It would appear that the pole would not be perpendicular to the ground since it is on a slope. I've attached a sketch, but there's not enough info to solve for $\theta$, if that is where $\theta$ is.
• Jan 12th 2009, 10:27 PM
magentarita
Yes....
Quote:

Originally Posted by masters
A diagram would be nice. It would appear that the pole would not be perpendicular to the ground since it is on a slope. I've attached a sketch, but there's not enough info to solve for $\theta$, if that is where $\theta$ is.

Nice picture but I think there is something missing from this question.