Geometry anyone?!?

[LightOn]

Hey all!

I have run into a Dilemma, I have forgotton my Geometry!!!

Can anyone help me find out the formula to get the degree of the angles in a triangle if you have the lengths of all sides of the triangle?

I have included a JPG So you have an idea of what I mean. I don't need the angles to this particular triangle it is just an example.

Edit In this case:
6 = a
8 = b
10 = c

[innocent]

sinA=opposite/hypotenuse
cosA=adjacent/hypotenuse
tanA=opposite/adjacent

so for example,
tan(the angle at the top)=6/8

Does that help? I hope that's what you meant.

[LightOn]

hmm. My Geometrical termonology is not up to standards.

Not sure if I am getting it. In this triangle the top (inside) angle is a 30 degree angle, and bottem right is 60 degree.

6, 8, and 10 are lengths of the lines in the triangle and 90 is the degree of the bottem left angle. If all 3 angles are added together the sum has to equal 180.

[Innova]

Correct, it should equal 180.

SinA = opposite/Hypotenuse

CosA = Adjacent/Hypotenuse

TanA = opposite/Adjacent

[IceQueen]

tanA=opposite/adjacent

so for example,
tan(the angle at the top)=6/10

6/8

[LightOn]

I am still lacking understanding of the formula used to get the angles. sin, cos, and tan all represent inside angles of the triangle? hypotenuse is line C (10) the line opposite of the right angle? After that I feel lost.

Man I have been out of school for too long or I didn't pay as much attention as I thought I did

A squared + B squared = C squared is how you get the third length, I know that much.

Reason why I am seeking for the formula is because I am building a project that will require precise cuts, angles included. My measurements are going to be a bit more difficult than 6, 8, and 10. But I do know 1 angle will be 90 degrees.

[innocent]

Originally posted by IceQueen
6/8

Oopsie.
corrected...

The opposite and adjacent side are relative to where the angle you're trying to figure out is. Opposite is opposite the angle, hypotenuse is the slanty one (as you knew) and adjacent is the one next to the angle that isn't the hypotenuse.

To work out the top angle use tan, using the formulae.
eg, tan(angle on top)= 6/8= 0.75
then press [shift tan] on the calculator (over the button [tan] there should be a function [tan -1]) to get the value of the angle.

[IceQueen]

I guess you're having a problem as what to do, after you've derived sin cos or tan.

First of all, you really need only one of those. Besides, calculating only one angle is already enough (the other unknown angle can be obtained by subtracting the known one from 90).

So you are left with something like
sin(A) = 6/10 = 3/5
I guess the question now is how do you get to A = x deg.
The answer is: you gotta do a trig table lookup for the decimal value of 3/5 (which is, incidentally, 0.6). There are trig tables with values of [url=http://www.grc.nasa.gov/WWW/K-12/airplane/tablsin.html]sin[/url], [url=http://www.grc.nasa.gov/WWW/K-12/airplane/tablcos.html]cos[/url] and [url=http://www.grc.nasa.gov/WWW/K-12/airplane/tabltan.html]tan[/url] for all positive angles.

So, looking up 0.6 in the table of sines, we get A = 37 deg.

Now, you can calculate B (the angle on the bottom), either by going 180-90-37 = 53

OR, do its sin.
Opposite for B will be 8, and hyp will be 10, so sin(B) = 4/5, which is 0.8 in decimal.

Do a sin table lookup (we are expecting to get 53), and what do we get? Yup. 53.

But I do know 1 angle will be 90 degrees.

Oh yeah. It wouldn't work otherwise.

[LightOn]

Ahhh yes...Windows Calculator has Scientific option. I got "it" now! Thanks Innocent, IceQueen and Innova....3 names that start with I .....which raises other questions I won't ask.

Thanks again!

[Innova]

ROFL, like what?

[LightOn]

[Innova]

I am so lost lol.

[sfalexi]

The big advantage here is that you have THREE different ways to calculate an angle. Since you know all three measurements, you can use ANY of SIN, COS, or TAN. When the test/quiz comes around watch out for them only giving you two sides and asking you to find all the angles and the third side.

Alexi

[sfalexi]

And watch out for one angle and one side and asking for the rest. And also watch out for being given two angles and asking what the ratio of the sides are. God I can't WAIT till I become a math teacher!

[Innova]

lol thats true...but I still wanna know what he was thinking rofl!