Answer: 0.
- A 0
- B 1
- C 2/sqrt(1-x<sup>2</sup>)
- D pi/2
Correct answer: A. 0
Explanation: Since sin-1(x) + cos-1(x) = pi/2 (a constant) for all x in [-1,1], its derivative is 0.
f(x)=|x| is perfectly continuous at x=0 (no break, no jump), but the curve has a sharp corner there: approaching from the left gives slope -1 and from the right gives slope +1 - since these one-sided derivatives disagree, the function is not differentiable at that point.
Concept context
When a function has no breaks (continuity) and when it has a well-defined slope (differentiability), plus rules for differentiating implicit, inverse trig, exponential, log, and parametric functions.