555

555 might be laughter in Thai internet slang—got it. Ready to study? Tell me your subject and level, and I can generate a quick mini-quiz or go over a tough concept.

Here’s a quick calculus warm-up (5 questions, with answers):

1. d/dx [sin x] = ?

• cos x

2. lim_{x→0} (sin x)/x = ?

• 1

3. d/dx [e^{2x}] = ?

• 2 e^{2x}

4. If f(x) = x sin x, then f'(x) = ?

• sin x + x cos x

5. ∫ x dx = ?

• x^2/2 + C

Want more questions, or a different subject (linear algebra, statistics, physics, etc.)?