Maths · Applications of derivatives: Rate of change of quantities, monotonic-Increasing and decreasing functions, Maxima and minima of functions of one variable

The two curves and

The two curves \( x^{3}-3 x y^{2}+2=0 \) and \( \mathbf{3} \boldsymbol{x}^{2} \boldsymbol{y}-\boldsymbol{y}^{3}-\boldsymbol{2}=\mathbf{0} \)

  • A. cut at right angles
  • B. touch each other
  • C. cut at an angle \( \frac{\pi}{3} \)
  • D. cut at an angle \( \frac{\pi}{4} \)

Step-by-step solution

Compute gradients: ∇f = (3(x^2-y^2), -6xy), ∇g = (6xy, 3(x^2-y^2)). Their dot product is 0, so normals are perpendicular, implying tangents are perpendicular. Hence curves cut orthogonally.
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