Pre-Calculus question????

Question

Find the trig functions of (-3/5, 4/5)

It is a unit circle

I know the hypotenuse is 1, but with SOHCAHTOA, I can't get 1!

Like for sine, I put 4/5 / -3/5 and I don't get 1!!

Answer 1

you are just confused with how SOHCAHTOA works.

for the triangle (-3/5, 4/5), the triangle is in the top left quadrant of the circle (quadrant 2). the vertical side is 4/5 in height, the horizontal side is 3/5 in length, and the hypotenuse is 1 or 5/5 in length. (you can find the length of the hyp using pythagoras' theorem, but it should always be 1 on a unit circle.) draw this triangle on a unit circle.

NOW, SOH means Sine uses Opposite over Hypotenuse. Opp = 4/5 = 0.8 and Hyp = 1. enter sin(0.8/1) in your calculator, and you will get the measure of the angle that points to the center of the triangle.

for the others: CAH: Cos(Adjacent/Hypotenuse)

TOA: Tan(Adj/Hyp)