Trap 1: Radians vs Degrees The limit sin = 1 ONLY when x is in radians. If x is in degrees, the limit is pi/180. JEE occasionally tests this distinction.
Trap 2: sqrt() = |x|, NOT x When x < 0, sqrt() = -x. This is critical for limits as x -> -infinity. For example, lim(x->-inf) sqrt()+x: since x < 0, sqrt() = -x, not x.
Trap 3: Greatest Integer Function Traps lim(x->0) [sin x/x] = 0, not 1. Since sin < 1 for small x, the floor function gives 0. Similarly, for x in (-1, 0), [x] = -1 (not 0).
Trap 4: Misapplying L'Hopital's Rule L'Hopital only works for 0/0 and infinity/infinity. Don't apply it to non-indeterminate forms. Don't use the quotient rule — differentiate numerator and denominator separately.
Trap 5: 1^infinity is NOT equal to 1 Many students assume 1^anything = 1. This is false for the 1^infinity form. Always use the exponential formula.
Trap 6: Continuity vs Differentiability f(x) = |x| is continuous at 0 but not differentiable. f(x) = x*sin (with f(0)=0) is continuous at 0 but not differentiable. Continuity does NOT imply differentiability.
Trap 7: One-sided behavior of e^ As x -> 0+, e^ -> infinity. As x -> 0-, e^ -> 0. This asymmetry is heavily tested.
Trap 8: Fractional Part near integers {x} approaches 1 from the left of any integer, but {n} = 0. Don't assume {x} -> 0 from both sides near an integer.