Pre-Calc 11 – Week 17 –

This week in pre-calc, I had some trouble understanding some concepts of trigonometry. So, I will share some tips on using sepcial triangles, circle chart, the CAST rule, and when to use the Cosine Law.

There are two special triangles the first having a 45 degree angle, a root 2 of the hypotenous, and 1 on the other lengths. The only option for this angle is to have45 degrees. The second special triangle is 60 degrees and 30 degrees, 2 on the hypotenous, root 3 on the adjascent and 1 on the opposite length. The two degrees for this triangle, are 30 and 60. For the circle chart, you can apply it to triangles that are 1, -1, 0 or undefined. The top and bottom quadrants are (0, 1) and (0, -1), while both sides are (-1, 0) and (1, 0). The degrees for the circle are 0, 90, 180, and 270. The CAST rule, begins in the fourth quadrant, with “C, then the first with “A”, then the second with “S”, then the third with “T”. In the first quadrant, all are positive (Cos, Sin, Tan). In the second quadrant, Sin is positive, and Tan and Cos are negative. In the third quadrant, Tan is positive, and Sin and Cos are negative. In the fourth quadrant, Cos is positive, and Tan and Sin are negative. You would decide to use th Cosine Law when there are two sides and one angle, which surround each other, makingĀ  “C shape.


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