If y = sin(x) + cos(x), then d²y/dx² at x = 0 = ?
Question 1
Q1. If y = sin(x) + cos(x), then d²y/dx² at x = 0 = ?
Answer: -1
Explanation: First derivative is cos(x) - sin(x), and the second derivative is -sin(x) - cos(x). At x = 0, -sin(0) - cos(0) = -1.