25. u = x^2 + yz, x = pr cos(theta), y = pr sin(theta), z = p + r;
Du/Dp, Du/Dr, Du/D(theta) when p = 2, r = 3, theta = 0
Du/Dp etc. are the partial derivatives.
Thanks.
you are correct.
by the chain rule: $\displaystyle \frac {du}{dp} = \frac {du}{dx} \cdot \frac {dx}{dp} + \frac {du}{dy} \cdot \frac {dy}{dp} + \frac {du}{dz} \cdot \frac {dz}{dp}$
for $\displaystyle \frac {du}{dr}$ replace p with r in the formula above
for $\displaystyle \frac {du}{d \theta}$ replace p with $\displaystyle \theta $ in the formula above