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April 18, 2015

April 18, 2015

Posted by **Tabby** on Sunday, April 22, 2012 at 9:23pm.

- Parametric to Rectangular? -
**Reiny**, Sunday, April 22, 2012 at 9:39pmfrom x = 5cos 2T ---> cos 2T = x/5

from y = -sin 2T ---> sin 2T = -y

we know sin^2 2T + cos^2 2T= 1

x^2 /25 + y^2 = 1

**x^2 + 25y^2 = 25**

(looks like we have an ellipse)

test:

let T = 30°

x = 5cos60° = 5(1/2) = 5/2

y = -sin60° = -√3/2

sub into the rectangular...

LS = 25/4 + 25(3/4) = 100/4 = 25

let T = 19.6°

x = 5cos39.2· = appr. 3.8747

y = -sin39.2 = appr. -.6320

LS = 3.8747^2 + 25(.6320)^2 = 24.99999

looks promising.

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