How do you convert r = 2tanthetasecthetar=2tanθsecθ into cartesian form?

1 Answer

By substitution y = 1/2*x^2y=12x2

Explanation:

First convert the expression into terms of cos(theta)cos(θ) and sin(theta)sin(θ)
r = 2*sin(theta)/cos(theta) *1/cos(theta)r=2sin(θ)cos(θ)1cos(θ)
rcos^2(theta) = 2*sin(theta)rcos2(θ)=2sin(θ)
Now the normal substitutions are x=rcos(theta)x=rcos(θ) and y=rsin(theta)y=rsin(θ)
:. sin(theta) = y/r and cos(theta) = x/r

Substituting these values into the expression above gives
r*(x/r)^2 = 2*y/r
cancel(r)*x^2/r^cancel(2) = 2*y/r
x^2 = r*2*y/r =2* y
:.y =1/2 x^2