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

1 Answer
BeeFree
Sep 26, 2015

Use the equation for the unit circle to solve for y.

Explanation:

The unit circle has a radius equal to 1 and is centered at the point (0,0). Therefore, the equation for the unit circle is:

x ^ 2+ y ^ 2 = 1

Now use the coordinates of point P and substitute into the above equation:

(-3/5) ^ 2+ y ^ 2 = 1

Next, solve for y:

y ^ 2 = 1 - (9/25) = 16/25

y = +- 4/5

Finally, we know from the problem that P lies in the second quadrant. In the second quadrant, X is negative and Y is positive. Therefore, the final answer is:

y = + 4/5

Hope that helps!

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