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Sum & Difference Formulas (5.2). JMerrill, 2009. Formulas for. (The signs are the same). (The signs are opposite). To Use the Formulas. Make up any 2 angles from the unit circle (to plug in for A and B) that equal the angle you are trying to find. Example:
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Sum & DifferenceFormulas (5.2) JMerrill, 2009
Formulas for (The signs are the same) (The signs are opposite)
To Use the Formulas • Make up any 2 angles from the unit circle (to plug in for A and B) that equal the angle you are trying to find.
Example: • Sin 15o can be sin(60o-45o) or sin(45o-30o)
Example • Find the exact value of sin15o • sin15o = sin(45o – 30o) = sin45ocos30o - cos45osin30o A = 45o, B = 30o
Example • Find the exact value of • Cosine or sine formula? Cosine!
Example • Find the exact value of • Sine or cosine formula? Sine!
You Do • Find the exact value of cos 75o
Last Example So, alpha is in QI, and beta is in QII
Remember • We know so all we need is 5 13 4 5 3 -12
Tan Formulas • (Notice that the sign of the numerator is the same as the sign of the formula; the denominator is the opposite sign.)
Example • Suppose and . Find Notice, they are NOT asking for the angles
You Do • Suppose
Example • Find the exact value of Go backwards—just like sine and cosine If they give you the right side of the equation, pick out alpha and beta and put them in the left side.
5 5 4 3 -3 -4
5 5 4 3 -3 -4
5 5 4 3 -3 -4