This week in Pre-Calculus 11, we’ve gone a lot more in-depth about trigonometry. We learned about angle rotation and how it you can find different ratios. One thing I found very interesting was how Sin= Y over R. This ratio is equivalent to Sin= O over H but most of the ratio’s we know from grade ten have changed this year.
What I wanted to talk about was the cast rule and how we can tell which ratio’s will be negative/positive just from looking where they are.
These are some notes I went over with my tutor but I really like the way he explained it. Pretty much we can just consider Sin = Y Cos = X and Tan as Y/X. This makes it a lot easier when we’re thinking about the value of our variables. Sin will always be positive in Q1 and 2 as that is where Y is positive. Cos will be positive in Q1 and 4 as X is positive there and Tan will be positive in Q1 and Q3. This Is also easy to remember using the CAST rule where Q1 is all Q2 is Sin Q3 is Tan and Q4 is cos but I think this way of thinking helps give a bit better understanding to it.