1. If the point P(4/5,y) lies on the unit circle and P is in the third quadrant, what does y equal?
2. There are values of t so that sin t = .3 and cos t = .6.
Is this statement true or false???
Thank you!
2 Answers

1)
16/25 + y^2 = 1
y^2 = 9/25
y = 3/5
2)
sin^2 t + cos^2 t = 0.3^2 + 0.6^2 = 0.45
this must equal 1 so this statement is false.

equation for unit circle is: x^2 + y^2 = 1
substituting the given x coord in this equation: y = +/ sqrt(1 – (4/5)^2) = +/ 3/5