# Thread: more hyperbolic function questions

1. ## more hyperbolic function questions

Hi

I need help on the following:

1)Given $sinh(u) = 2 and sinh(u) = 7 evaluate sinh(u-v)$

I used $sinh(u-v) = sinh(u)cosh(v) - cosh(u)sinh(v)$ but still was not unable to get the final values.

2) Given the parmaetric equations x=2cos(t), y=3sin(t) use the identity $cos^2(t) + sin^2(t) = 1$

This is what i have done:
$
2x^2 + 3y^2 = 1$

Can someone tell me why this is incorrect and this is correct:
$\frac{x^2}{4}+\frac{y^2}{9} = 1$

P.S

2. For the second one:

$\frac{x}{2}=cos(t)$ and $\frac{y}{3}=sin(t)$

so,

$\left (\frac{x}{2}\right)^2=cos^2(t)$ and $\left ( \frac{y}{3}\right )^2=sin^2(t)$

$\therefore \frac{x^2}{4}+\frac{y^2}{9}=1$