Hatrack River Forum: I need math help

This is topic I need math help in forum Books, Films, Food and Culture at Hatrack River Forum.

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Posted by Starsnuffer (Member # 8116) on :

Find measure of vertex angle in iso. triangle with sides 22 22 and 28

I don't know how to do it.

Posted by King of Men (Member # 6684) on :

42.

No, seriously. It comes to 79 degrees.

Posted by Starsnuffer (Member # 8116) on :

please explain how

Posted by Dagonee (Member # 5818) on :

Hint: Draw a line from the vertex perpendicular to the baseline. You now have two right triangles to work with and the lengths of the sides of those triangles.

That should be a plenty big enough hint.

Posted by Starsnuffer (Member # 8116) on :

Wow, I feel like a retard, ive been working on this for like 15 minues plus.

Posted by Airguitarist (Member # 2647) on :

You could also use the Law of Cosines:

A^2=B^2+C^2-2*B*C*cos(alpha)

Where A, B and C are the lengths of the sides of the triangle, and alpha is the angle oposite side A. Since you want to find the vertex, you would use A=28, B=22 and C=22, then use the inverse cosine function to solve for the angle.

(edit): wow, you guys are fast.

Posted by Dagonee (Member # 5818) on :

Starsnuffer, once you calculate it, please post what you got for whichever trig ratio you used and the final angle. Now I'm curious, but I don't want to do the math. [Smile]