Posts in MAT 17A
Infinity and DNE in Limits

The best way to approach why we use infinity instead of does not exist (DNE for short), even though they are technically the same thing,  is to first define what infinity means.

Infinity is not a real number. It's a mathematical concept meant to represent a really large value that can’t actually be reached. In terms of solutions of limits, it means that the equation you are taking the limit of will go in that direction forever.

Shayan R.
Related Rates

Whenever you start a related rates problem (or most word problems) it's a good idea to:

• Define a coordinate system: For this we can use the usual: it’s positive if it’s moving to the right or up.  This is to make sure we don’t miss a negative sign somewhere.

• Draw out the system in question:

Shayan R.
Optimization

Optimization refers to the maximums or minimums of a function in calculus.
Common types of optimization problems include:

• Optimization Area & Perimeter

• Optimization Volume & Surface Area

• Optimization of the Distance Between a Point on a Curve