Sum and Difference Formulas

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Sum and Difference Formulas
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Learning Goal

• I will be able to use sum and difference formulas
  to rewrite and evaluate trigonometric functions.

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Project Mathematics Video
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Sums and Differences
sin (A B) sin A cos B sin B cos A sin (A
B) sin A cos B sin B cos A cos (A B)
cos A cos B sin A sin B cos (A B) cos A cos
B sin A sin B
Sine shares and has same sign
Cosine clique-ish and has contrary sign
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Simplify
cos 3x cos 2x sin 3x sin 2x cos (3x 2x)
cos x
sin 105 cos 15 - cos 105 sin 15 sin (105
- 15) sin 90 1
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Find
Suppose sin a 4/5 and sin q 5/13 where 0 lt a
lt 90 and 90 lt q lt 180 . Find the value of cos
(a q).
cos (a q) cos a cos q - sin a sin q
(3/5)(-12/13) - (4/5)(5/13) -36/65 - 20/65
-56/65
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Expand
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Sum and Difference
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Simplify
tan (30 15) tan 45 1
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Learning Goal

• I will be able to use sum and difference formulas
  to rewrite and evaluate trigonometric functions.

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End of notes.

• Homework Making Practice Fun 81