2. It’s either sine, cosine, or tangent.

4. Three of these are all the same value.

6. The sine of one angle is the cosine of the other angle.

9. It’s best if you simplify, but not required in this case.

12. See #6.

21. Start with sin 71° or cos 71°, because you know the length of the hypotenuse and sine and cosine both use the hypotenuse.

23. After setting up the initial equation, multiply both sides by the denominator, whether it is a number or a variable.

26. Two of the ratios are 2 over 4.

27. Try each possibility, and simplify to see if equals √3/2.

30. Change the function, or change the ratio.

31. Set up sine, cosine, or tangent equation with one variable, and multiply each side by the denominator.

48. Both are correct (explain why).

53. To divide by a fraction, multiply by its reciprocal.