Double angle formulae

**sakuraxkisu** · October 3rd 2011, 12:31 PM

Hi, I have a question on double angle formulae:
Eliminate theta from the equation
x = 2 sec theta, y = cos 2 theta

The answer is x^2y = 8 - x^2

Thank you!

**skeeter** · October 3rd 2011, 02:42 PM

Originally Posted by sakuraxkisu

Hi, I have a question on double angle formulae:
Eliminate theta from the equation
x = 2 sec theta, y = cos 2 theta

The answer is x^2y = 8 - x^2

$x = 2 \sec{\theta} \implies \cos{\theta} = \frac{2}{x}$

$y = \cos(2\theta) = 2\cos^2{\theta} - 1$

proceed ...

**sakuraxkisu** · October 5th 2011, 01:41 PM

Thank you so much! I feel like a bit of an idiot as that was so simple haha

Thread: Double angle formulae

LinkBack

Thread Tools

Display

Double angle formulae

Re: Double angle formulae

Re: Double angle formulae

Similar Math Help Forum Discussions

Double Angle Formulae

problem in addition formulae and double angle formulae

Simple double angle formulae

Double angle formulae

R formulae (double angle formulae) URGENT

Search Tags