# Polar equations - Help?

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i need to graph the polar equation
2 = r cos (theta + 180) on one of the graphs that looks like a flattened globe.

So far I have
2=r cos180 costheta + r sin180 sintheta
what do i do now?

• Polar equations - Help? -

Isn't cos(Theta+180)= -cosTheta ?
checking the hard way...

cos(A+B)=cosAcosB-sinAsinB
cos(Theta+180)= cosThetacos180-sinThetasin180= -cosTheta.

2= -rcosTheta

r= -2/cosTheta.

Graph it.

• Polar equations - Help? -

thank you so much, I don't know how i missed that identity.

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