Pre-Calculus For Dummies, 2nd Edition

Chapter 10

Taking Charge of Oblique Triangles with the Laws of Sines and Cosines

In This Chapter

Mastering the Law of Sines

Wielding the Law of Cosines

Utilizing two methods to find the area of triangles

In order to solve a triangle, you need to find the measures of all three angles and the lengths of all three sides. Three of these pieces of information are given to you as part of the math problem, so you need to find only the other three. Up until now throughout this book, we work in depth with right triangles. In Chapter 6, we help you find the lengths of missing sides by using the Pythagorean theorem, find missing angles by using right-triangle trigonometry, and evaluate trig functions for specific angles. But what happens if you need to solve a triangle that isn’t right?

You can connect any three points in a plane to form a triangle. Unfortunately, in the real world, these triangles won’t always be right triangles. Finding missing angles and sides of oblique triangles can be more confusing because they don’t have a right angle. And without a right angle, the triangle has no hypotenuse, which means the Pythagorean theorem is useless. But don’t worry; this chapter shows you the ...