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Corollaries

1. If b^{2 }+ c^{2 }³ a^{2 } , then cos A ³ 0 \ Ð A is acute

2. If b^{2 }+ c^{2 } £ a^{2 }, then cos A £ 0 \ Ð A is obtuse

3. If b^{2 }+ c^{2 } = a^{2 }, 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