Thread: Pre-Exam Review: Trig is killing me

I hope you guys can help me! If I don't get a 75% on this exam I fail, and will not graduate.

I'm having trouble clicking with Trig. I have the info recorded such as;

Use Soh-Cah-Toa for right angled triangles
Use Sine Law for ASS or ASA
Use Cosine Law for SSS or SAS

But when I look at a question I just freeze and don't know what to do.

This one for example;

A stencil is made out of plastic. What is the are of the plastic? The inner design is an equilateral triangle, inside a larger equilateral triangle, inside a square.

I made a not-so-good drawing to try and help;


If someone could please explain how to solve this I will be extremely happy ... until my next question.

The area of a triangle can be obtained by:



or



Try using the second formula, where c is the angle between the sides a and b.

Post what you get.

I prefer not doing the calculations, because I don't quite understand your question. I especially don't know what the square has to do with the area of the triangle...

EDIT: Remember that in an equilateral triangle, all the angles within the triangle are 60 degrees, so c = 60