This week we learned more about triangles and the ratio (i.e. Sine, Cosine, Tangent) in the triangle.

For me, the hardest part is to solve problems using special triangles, because when the reference angle is a special angle– for example, 45, 60, etc.– there’s always 4 kinds of degrees for each special angle, you need to figure out which is belong to which and also need to know the sign of them (positive or negative).
And there’s another kind of questions made me feel hard to deal with, which is letting you determine the degree of some angle whose sin/cos/tan equals others.

For example, if sin 245= sin A, determine sin A.
There’re a few steps to solve this problem.
First, we need to draw an angle to know which quadrant this angle is in, 245 is in quadrant three, according to “All Students Take Calculus” rule, the tangent of this angle should be negative. So sin A is also negative.
Second, we need to know the reference angle of this angle, it’s 245-180=65, so now we know that the sin of an angle who has a reference angle 65 is negative, so the other angle is in quadrant4, which is 360-65=295. So a=295

I also learned some new words, such as rotation angles, quadrant, opposite, adjacent, hypotenuse, terminal arms, clockwise…… I found that math is really an interesting subject.