4. (Textbook Exercise 2.3.87.c) Using the derivative d formulas sin(x) = cos(x) and dx d cos(x) = dx d = - sin(x), apply the quotient rule to obtain cot(x) dx cos(x) cot (x) = sin(x) = - csc (x). (Hint: Recall . Apply the quotient rule.) 5. (Textbook Exercise 2.3.87.a) Use the same techniques from problem (4) above to show sec(x) = sec(x) tan(x). d dx 6. (Optional Bonus Question, worth up to 3 bonus points) Textbook Exercise 2.2.108: Let (a, b) be an arbitrary point on the graph of y = 1, x > 0. X Prove that the area of the triangle formed by the tangent line through (a, b) and the coordinate axes is 2.