Corollaries

1. If b² + c² ³ a² , then cos A ³ 0 \ Ð A is acute

2. If b² + c² £ a² , then cos A £ 0 \ Ð A is obtuse

3. If b² + c² = a² , then cos A = 0 \ Ð A is a right angle

4.   a = b cos C + c cos B

       b = c cos A + a cos C

       c = a cos B + b cos C

This rule is known as "Projection rule."

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Index

3. 1 Solving Right Triangles
3. 2 Law of Cosines
3. 3 Law of Sines
3. 4 The Ambiguous Case of Law of Sines
3. 5 Areas of Triangles
Supplementary Problems

Chapter 4