Step-by-step explanation:
(i) We know that [tex]x = r\cos{\theta}\:\text{and}\:y = r\sin{\theta}.[/tex] So we can write the given equation as
[tex]r^2\cos^2\theta - r^2\sin^2\theta = 5[/tex]
[tex]\Rightarrow r^2(\cos^2\theta - \sin^2\theta) = 5[/tex]
[tex]r^2 = \dfrac{5}{(\cos^2\theta - \sin^2\theta)}[/tex]
[tex]\:\:\:\:\:=\dfrac{5}{\cos{2\theta}} = 5\sec{2\theta}[/tex]
(ii) Recall that
[tex]\cot{\theta} = \dfrac{\cos{\theta}}{\sin{\theta}}[/tex]
[tex]\csc{\theta} = \dfrac{1}{\sin{\theta}}[/tex]
so we can write r as
[tex]r = 8\cot{\theta}\csc{\theta}[/tex]
[tex]\:\:\:\:= 8\left(\dfrac{\cos{\theta}}{\sin{\theta}}\right)\left(\dfrac{1}{\sin{\theta}}\right)[/tex]
[tex]\:\:\:\:= 8\left(\dfrac{x}{y}\right)\!\left(\dfrac{r}{y}\right) = \dfrac{8xr}{y^2}[/tex]
Upon simplification, we get
[tex]y^2 = 8x[/tex]
