Find the missing coordinate of P, using the fact that P lies on the unit circle in the given quadrant. P(____, -20/29) quadrant IV

Question

Find the missing coordinate of P, using the fact that P lies on the unit circle in the given quadrant.

P(7/8,____)quadrant I

Answer 1

equation for a circle is

(x-h)^2 + (y-k)^2 = r^2

where (h,k) = center and r= radius

for a unit circle centered at the origin

the equation is x^2 +y^2 = 1 and x=+/-sqr(1-y^2)

if y= -20/29 then x= sqr(1- 400/841) = 21/29 for Q4

if x= 7/8, then y = sqr(1-49/64) = (sqr15)/8 for Q1

x is positive for Q1 or 4, so ignore the negative square roots