Question

Eliminate the parameter and write the corresponding rectangular equation whose graph represents the curve.

x = sec Q
y = cos Q

x^2 + y^2 = 1/cos^2 + sin^2/cos^2 =
x^2(1 +sin^2) = x^2(2-cos^2)

x^2(2-1/x^2) = 2x^2 - 1

x^2 - y^2 = 1

My teacher said to use secant*cosine = 1. Please explain!!

Answer 1

Isn't sec x = 1/cosx ??

so isn't (secQ)(cosQ)
= (1/cosQ)(cosQ) = 1 ???

so we know
secQ(cosQ) = 1
xy=1

looks like we got our equation!