BillyK

Not to different to normal differentiation, just have to treat the variable that your not differentiating as a constant.

$\frac{\delta F}{\delta x} = \frac{4y(y^2-x^2)}{(x^2+y^2)^2}$

and

$\frac{\delta F}{\delta y} = \frac{4x(x^2-y^2)}{(x^2+y^2)^2}$

through the use of quotient rule.

My apologies, I misread the question. looks like the guest that replied is correct though. Somehow read it as cos and solved it as cos but wrote sign, been a long day.

2.218 to 3 siginificant figures, anything after7 is really a tiny change as factorials grow incredibly quickly therefore you can ignore any values after 7/7! and be within a reasonable uncertainty.

Re-arrange to get the equation equal to 0.

$4cos^2(\theta) + 9sin(\theta) - 6 = 0$

Solve like any other quadratic equation.

$cos(\theta ) = \frac{-9\frac{+}{-}\sqrt{81 - 4(4*(-6))}}{8}$

And you should be able to get it from there.

2478m * 0.6m = 1486.8m^2

250/4 = 125/2 = 62.5