Is It Possible? Solving Calculus Questions with Ease

  • Level: Undergrad 
  • Thread starter NODARman
  • Start date
  • Tags Tags
    Calculus
2 replies · 2K views · last reply
NODARman
Messages
57
Reaction score
11
TL;DR
.
Hi, just wondering if that's possible in calculus.
(See the attachment)
 
Attachments
  • Handwritten integral from 0 to 2π of πR dθ over 180 dt, with dt struck out in red and the red rewritten as the integral from 0 to 2π of πR over 180 dθ.
    166920054969935055318737542524.jpg
    37.6 KB · Views: 209
NODARman said:
TL;DR Summary: .

Hi, just wondering if that's possible in calculus.
(See the attachment)
What you wrote was essentially correct. But...

In reality? No. The derivative notation ##\dfrac{d \theta }{dt}## is not actually a fraction so you cannot cancel the dt's.

However, in practice you can "cancel" the dt's. It's a similar effect to the chain rule: ##\dfrac{d \theta }{dx} = \dfrac{d \theta }{dt} \cdot \dfrac{dt}{dx}##. Again, there is no real cancellation, but it appears that way.

Mathematicians in the 1800s spent a great deal of time showing how you can treat a differential element as a fraction. Most of the time you can get away with it.

-Dan
 
  • Like
Likes   Reactions: scottdave, DaveE, vela and 1 other person
Technically the bounds on the integral need to change to ##\int_{t(0)}^{t(2\pi)}## if you are integrating wrt ##t##.
 
  • Like
Likes   Reactions: DaveE and topsquark