This is the section where you learn the relationships among functions and how to solve more difficult trigonometric functions. The relationships you will learn will be reciprocal, Pythagorean, cofunction, or relationships with negatives. All of the relationships come back to haunt you in the last part of this section, Solving More Difficult Trigonometric Functions, and in the next section, Triangle Trigonometry. This means learn these relationships well. If you learn nothing else in this section, pay special attention to the Pythagorean Realtionships.