# Partial Derivatives

## 4422 days ago by pub

var('x y u v')
 (x, y, u, v) (x, y, u, v)
plot3d((x^2 - y^2) / (x^2 + y^2), (x, -1, 1), (y, -1, 1))
f(x, y) = x^3 + x^2 * y^3 - 2 * y^2 P = plot3d(f(x, y), (x, 1, 3), (y, 0, 2), opacity = 0.2) P += parametric_plot3d([2 + u, 1, f(2, 1) + diff(f(x, y), x)(x = 2, y = 1) * u], (u, -1/2, 1/2), color = "red", thickness = 2) P += parametric_plot3d([2, 1 + u, f(2, 1) + diff(f(x, y), y)(x = 2, y = 1) * u], (u, -1/2, 1/2), color = "green", thickness = 2) P += point((2, 1, f(2, 1)), color = "black", size = 10) show(P)
f(x, y) = 4 - x^2 - 2 * y^2 P = parametric_plot3d([u * cos(v), 1 / sqrt(2) * u * sin(v), 4 - u^2], (u, 0, 2), (v, 0, 2 * pi), aspect_ratio = [1, 1, 1], opacity = 0.2) P += parametric_plot3d([1 + u, 1, f(1, 1) + diff(f(x, y), x)(x = 1, y = 1) * u], (u, -1/2, 1/2), color = "red", thickness = 2) P += parametric_plot3d([1, 1 + u, f(1, 1) + diff(f(x, y), y)(x = 1, y = 1) * u], (u, -1/2, 1/2), color = "green", thickness = 2) P += point((1, 1, f(1, 1)), color = "black", size = 10) show(P)