If the point P(-3/5, y)lies on the unit circle and P is the third quadrant, what does y equal?

Question

anonymous · Answer

@misty1212 @jim_thompson5910

jim_thompson5910 · Answer

P lies on the unit circle, so we know that x^2 + y^2 = 1

jim_thompson5910 · Answer

x = -3/5 is given to you

use this to find y

jim_thompson5910 · Answer

P is the quadrant 3, so y will be negative

jim_thompson5910 · Answer

does all that make sense? or no?

anonymous · Answer

so far yes

jim_thompson5910 · Answer

so you need to solve for y

$$\Large x^2 + y^2 = 1$$

$$\Large \left(\frac{-3}{5}\right)^2 + y^2 = 1$$

$$\Large \frac{9}{25} + y^2 = 1$$

$$\Large y = ???$$

anonymous · Answer

I got 4/5 and -4/5

misty1212 · Answer

HI!!

anonymous · Answer

hi!

misty1212 · Answer

what is the most famous right triangle of all time?

anonymous · Answer

45 45 90?

misty1212 · Answer

lol those are angles silly
i meant the one with the nice integer sides

jim_thompson5910 · Answer

y = -4/5 is your answer because remember P is in quadrant 3

jim_thompson5910 · Answer

y is negative in quadrant 3

misty1212 · Answer

|dw:1422238684351:dw|

misty1212 · Answer

divide everything by $5$ and you get this |dw:1422238741718:dw|

misty1212 · Answer

since your first coordinate was $\frac{3}{5}$ the second one had to be $\frac{4}{5}$ or maybe $-\frac{4}{5}$ depending on the quadrant