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Hello everybody.
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In this video, i'm going to be showing you how to solve exercise 18 in chapter 9, section 1 of cohen's pre -calculus 7th edition.
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Now, in this problem, they want us to use the second edition formula for sign to compute the quantity sine of pi over 12.
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Now, to do this, the first thing we want to do is recognize that this term pi over 12 is equal to 4 pi over 12 minus 3 pi over 12.
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And these fractions themselves can be reduced to pi over 3 and pi over 4.
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And so we have that pi over 12 is equal to pi over 3 minus pi over 4.
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And this is important because each of these individual angles here can be identified explicitly when plugged in to sign and cosine functions.
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And so with this, what we want to do is recall the second edition formula for sign, which deals with subtractions in its argument.
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We have that for two angles, s and t, the sign of s minus t is equal to the sign of s times the cosine of t minus the cosine of s times the sine of s times the sign of t...