Common Mistakes
Frequent Errors
1. Evaluating sec where cos = 0 or csc where sin = 0 (3.11.A.1/A.2). 2. Claiming sec or csc can equal 0.5 (3.11.A.3). 3. Asymptotes for sec/csc at wrong angles (not cos/sin zeros). 4. Graphing sec/csc without gaps at asymptotes. 5. Cot asymptotes at cos = 0 instead of sin = 0 (3.11.A.5). 6. Forgetting cot decreases between asymptotes (3.11.A.5). 7. Confusing cot with tan graph shape. 8. Missing that cot = cos/sin, not sin/cos (3.11.A.4).
Why These Happen
Students focus on forward trig graphs and treat reciprocals as "the same but bigger."
How to Fix Them
- Always list denominator zeros first.
- Compare |sec| and |cos| at the same angle.
- Sketch asymptotes before curves.
Avoidance Scripts
- "Denominator zero means undefined."
- "sec/csc live outside (-1, 1)."
- "cot breaks where sin = 0."
Quick Self-Check
- Did I check cos != 0 for sec and sin != 0 for csc/cot?
- Are asymptotes at the right zeros?
- Is |output| >= 1 for sec/csc when defined?