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

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Answer 1 · 2016-11-15T23:15:04

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

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.