Posted by **Mary** on Monday, January 19, 2009 at 4:03am.

Graph the polar equation: 2=r cos(theta + 180)

2=r(costheta cos180+sintheta sin180)

2=r(1/2costheta +pi+ pi sintheta)

2=1/2rcostheta + pi rsintheta

2=1/2x+ pi y

4=x+ pi

0= x + pi-4

how do i graph?

- pre-calculus -
**Damon**, Monday, January 19, 2009 at 6:19am
trig identity is

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

I think you have the sign wrong.

use pi radians for 180 deg

let t = theta

2 = r (cos t cos pi - sin t sin pi)

cos pi = -1 and sin pi = 0

2 = r (- cos t)

r cos t = -2

x = -2

vertical line through x = -2

note y = r sin t

so y = (-2/cos t)sin t

y = -2 tan t

tan t takes all values from -oo to +oo as t goes from 0 to 2 pi. In other words the entire vertical line.

- pre-calculus -
**Mary**, Monday, January 19, 2009 at 6:43am
Thank you I understand now.

- xwao evroyiasq -
**xwao evroyiasq**, Sunday, February 1, 2009 at 10:05pm
kgovslri puljv nemdh eftio guos ouivrzye ztryihecl

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