How do you graph the polar equation 3=rcos(theta+90^circ)?

1 Answer
Nov 15, 2016

Draw a horizontal line that crosses the y-axis at -3.

Explanation:

Use the sum of two angles identity:

cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

To discover that:

cos(theta + 90^@) = -sin(theta)

Make that substitution:

3 = -rsin(theta)

Flip and multiply by -1

rsin(theta) = -3

Substitute y for rsin(theta):

y = -3

Draw a horizontal line that crosses the y-axis at -3.