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Student is seeking guidance on completing a complex differentiation problem involving multiple variables and derivatives | Step-by-Step Solution

PhysicsCalculus
Explained on January 12, 2026
📚 Grade college🔴 Hard⏱️ 20+ min

Problem

Problem with differentiating a mathematical expression, specifically involving second derivative calculations with r and theta, where student is missing certain terms in the final solution

🎯 What You'll Learn

  • Master complex differentiation techniques
  • Understand derivative calculations in polar coordinates
  • Learn handling of multiple varying parameters

Prerequisites: Calculus fundamentals, Trigonometry, Chain rule, Polar coordinate systems

💡 Quick Summary

Hey there! I can see you're working on a challenging differentiation problem with polar coordinates - these problems can definitely be tricky because r and θ are often both changing with respect to time, creating some sneaky interdependencies. When you're finding second derivatives in polar systems, have you made sure to apply both the product rule and chain rule systematically to every single term? Think about this: when you differentiated your first derivative terms, did each term that contained both r and θ components generate all the possible combinations of derivatives? The missing terms you're looking for are most likely those "cross terms" where the derivatives of r and θ interact with each other - like when you differentiate something involving both ṙ and θ̇ together. I'd suggest going back through each first-derivative term and carefully applying the product rule again, paying special attention to any terms where r and θ derivatives appear together. You've got the fundamental approach down, so trust your calculus skills and just be extra methodical about catching all those interconnected pieces!

Step-by-Step Explanation

What We're Solving:

You're working on a complex differentiation problem involving both r and θ (polar coordinates), specifically calculating second derivatives where you're missing some terms in your final solution.

The Approach:

When dealing with expressions in polar coordinates (r, θ), we need to be extra careful because both variables can depend on other parameters (like time). The key is to systematically apply the chain rule and product rule, making sure we don't miss any "hidden" derivatives that come from the interdependence of r and θ.

Step-by-Step Solution:

Step 1: Identify what each variable depends on

  • Clearly write out what r and θ are functions of (usually time t)
  • Remember: r = r(t) and θ = θ(t)
Step 2: For the first derivative, apply the chain rule systematically
  • When differentiating expressions with both r and θ, each term may generate multiple derivative terms
  • Don't forget that ṙ (dr/dt) and θ̇ (dθ/dt) both exist!
Step 3: For the second derivative, use the product rule on EVERYTHING
  • Each first-derivative term needs to be differentiated again
  • Terms like ṙ will become r̈, and terms like θ̇ will become θ̈
  • Mixed terms (involving both r and θ derivatives) often appear here!
Step 4: The most commonly missed terms
  • Cross derivatives: When you have terms like r·θ̇, the second derivative gives you both ṙ·θ̇ AND r·θ̈
  • Double product rule applications: Terms involving products of derivatives often generate more terms than expected
  • Chain rule on composite functions: If you have trigonometric functions of θ, remember cos(θ) becomes -sin(θ)·θ̇

The Answer:

Without seeing your specific expression, I can tell you that second derivatives in polar coordinates typically include:
  • Pure r terms: r̈
  • Pure θ terms: θ̈
  • Mixed terms: combinations of ṙ, θ̇, and their products
  • The missing terms are most likely the mixed derivative terms where r and θ derivatives interact!

Memory Tip:

Think of it like unwrapping a gift with multiple layers - each time you differentiate, you're unwrapping another layer, and polar coordinates have "hidden connections" between r and θ that create extra terms. Always ask yourself: "Did I account for how BOTH r and θ change?"

⚠️ Common Mistakes to Avoid

  • Forgetting to apply chain rule correctly
  • Missing terms in complex derivative calculations
  • Mishandling coordinate system transformations

This explanation was generated by AI. While we work hard to be accurate, mistakes can happen! Always double-check important answers with your teacher or textbook.

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📷 Problem detected:

Solve: 2x + 5 = 13

Step 1:

Subtract 5 from both sides...

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