Question: Geometry

Geometry

How do I find an unknown angle of a triangle given two sides?

Date Posted: November 01, 2007 Tagged Under: geometry . Math . mathematics
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I need to know the info given and what type of triangle.

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You can't. You need more information. Trig functions will only work if it's a right triangle (in which case you know two sides and an angle). You need two sides and an angle or all 3 sides. Try this to prove it: draw one of the side lengths. Then, at the end of that side, draw at any angle a segment of the second side length. Now finish drawing that triangle. Next, draw the second side but at any different angle. Can you still draw a triangle? So you've now got two triangles with two of the same side lengths. As soon as you can make two triangles (you can actually make an infinite number of triangles, but two is what matters), you can't find the angle because it could be either.

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Use one of your trig functions.
Sohcahtoa (Sine, Cosine, Tangent)

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does it tell you what kind of triangle it is like isosceles, equilateral or is that all they give you???

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Like Juke said, it depends on the angle you are wanting and what two sides are given... This is kind of hard to explain without getting to draw an example... so please bear with me. Lets say they give us 3 as the side that is opposite of the angle that we are looking for and 6 as the side that is the hypotenuse of the angle we are looking for. We would use the sine function with this equation because it involves the opposite and the hypotenuse.... We would set up the equation as so: sin x = 3/6
We could simplify 3/6 to 1/2... sin x = 1/2 And if you don't know your angles very well... All you have to do is punch this in your calculator as arcsin 1/2 and it will give you the answer... but basically all it is asking you for is what angle of sine gives you 1/2 and the answer you should get is 30 degrees or pie/6 depending on if you use degrees or radians...
I really wish I could show you how to do this on a board or something where you could visualize it better... Well I hope this helps..

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It depends on which two sides you have. But in general you will need to use the trigonemetric functions such as sin, cos, tan.

sin= opp/hyp
cos-adj/hyp
tan=opp/adj