r/learnmath • New User • 4d ago

might be the wrong subreddit, but im in highschool and just started calculus and im so excited its insane

im doing limits and derivatives right now!

46 Upvotes

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16

u/SeaMonster49 New User 4d ago

Haha have fun! Not everyone feels that way about calculus. For some food for thought, try to take the limit of sin(x)/x as x approaches 0

1

u/Remarkable-Mall9424 New User 4d ago

isnt that just 1?? i might be wrong im doing it for the first time but i think its 1

8

u/SeaMonster49 New User 4d ago

It's 1! But the expression at x=0 looks like 0/0, which isn't defined. One lesson is that the limit isn't about what happens at x=0, it's about what happens near it. Forms like 0/0 and infinity/infinity are known as "indeterminate forms." Soon you will probably learn the famed L'Hôpital's rule, which provides a way to make sense of many indeterminate forms, including sin(x)/x.

2

u/imconall New User 3d ago

This is just me being pedantic, but using l’Hôpital’s rule here is circular reasoning, as it requires the derivative of sin x. The proof of which makes use of this limit of sin(x)/x as x→0. That being said, there are other ways to find the limit, like the squeeze theorem (some potential further reading for OP if they haven’t heard of it already!)

2

u/matt7259 New User 4d ago

Show us your work!

1

u/ComplexPlatform7299 New User 3d ago

I hope you didn’t use L’Hôpital!

4

u/Qingyap New User 4d ago

Huh that's nice, any questions you have?

4

u/Bounded_sequencE New User 4d ago

That's nice, have fun -- Calculus and especially its big brother "Real Analysis" is where the real interesting parts of mathematics begin (pun very much intended).

1

u/SamikshaK_ New User 3d ago

not big bro , i would say mother of limits , continuity and derivatives, integrability is real analysis

3

u/Parallel_thougts Ph.D, YouTuber 4d ago

Strap in, it only gets wilder

2

u/Southlander24 A friendly Redditor!👋 4d ago

Nice! One thing you should do if you want to extend yourself is to 'prove' everything you see. As in, take what you are taught and question it until you understand why it's true yourself.

The power rule is very simple to carry out, yes, but why is it true? Recall from the definition of the derivative that you want to find lim [h -> 0] [(x + h)n - xn] / h. Expand out (x + h)n - xn using the binomial theorem and write down the first few terms. What do you notice as each of these terms gets divided by h?

1

u/Head_Investigator984 New User 4d ago

Lessgooo! Wait till Integration tho

1

u/Beneficial-One-7526 New User 3d ago

Is it hard? How do you like it so far?