Homework Help: Geometry

Posted by Angela on Saturday, August 23, 2008 at 12:06pm.

x
________________<20*
|<90*
y |
|<70*

(hypotenuse length is 12 units)

I'm learning about trig ratios, and my dad was trying to compare it to a circle or something? All I know is
sin = a/c
cos = b/c
tan = a/b

you're trying to figure out the proportions of the lengths of the triangle relative to its angles, actually the other way around in this case.

In accordance with the ratios I listed above,
side A is opposite angle A
side B is opposite angle B
side C is opposite angle C

so, in this case, the right angle is <C and the hypotenuse is side C

thus, does: ?
sin = y/12
cos = x/12
tan = y/x

Now I'm a little confused on how to bring in the angles, and how do I know whether to use sin,cos, or tan?
_______________________________________________

What happens with a problem where I know 2 of the sides, and that it's a right triangle? I then have to figure out the other two angles x and y.

I can figure out the length of the third side using the Pythagorean theorem, but how to I reverse to figure out the angular proportions from the lengths?

Thanks

Geometry - Reiny, Saturday, August 23, 2008 at 12:32pm
your Dad is making the connection between the "unit circle" and basic trigonometry.

Do a Google search for "unit circle" or "trigonometry and the unit circle"
You will get many webpages, here is one that seems to be quite good

http://www.humboldt.edu/~dlj1/PreCalculus/Images/UnitCircle.html

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