Choose a new chapter
About ClassZone  |  eServices  |  Web Research Guide  |  Contact Us  |  Online Store
ClassZone Home
McDougal Littell Home
Algebra 2
Home > Algebra 2 > Chapter 13 > 13.6 The Law of Cosines > 13.6 Problem Solving Help
Return to book index Chapter 13 : Trigonometric Ratios and Functions
13.6 Problem Solving Help

Lesson 13.6: Help for Exercises 30-37 on page 811

Determine the relationships between the given sides and angles. Draw (don't be too concerned with making the sides and angles exact), then use the given information to determine if the law of cosines, law of sines, or Pythagorean theorem applies.

Use the law of cosines for cases when you have SAS or SSS. After you apply the law of cosines once to find a side or angle, you can use the law of sines and the fact that the angles in a triangle add up to 180° to solve the remainder of the triangle. The law of cosines is stated on page 807. Use the law of sines for cases when you have ASA, AAS, or SSA. Refer to the Homework Help note for Lesson 13.5 if the triangle falls under the category of SSA. The law of sines is stated on page 799.

If the triangle has a 90° angle, then you can use the Pythagorean theorem and right triangle trigonometry to solve the triangle. Trigonometric functions for right triangles can be found on page 769. Look back at Examples 1-3 on pages 769 and 770 for help with the Pythagorean theorem and right triangle trigonometry.