Question

Find the exact value of the expression. Do not use a calculator $8 \cos 45^\circ - 7 \sin 45^\circ$ 

          Find the exact value of the expression. Do not use a calculator
$8 \cos 45^\circ - 7 \sin 45^\circ$
Find the exact value of the expression. Do not use a calculator 8 cos 45^∘ - 7 sin 45^∘

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Precalculus with Limits
Precalculus with Limits
Ron Larson 2nd Edition
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Find the exact value of the expression. Do not use a calculator 8cos45deg -7sin45deg Find the exact value of the expression Do not use a calculator 8cos45-7sin45
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Transcript

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00:01 In order for us to solve this, we need to come with a combination of values that's going to get us pi over 12 that are on unit circle.
00:06 For example, i can rewrite this as 4 pi over 12 minus 3 pi over 12.
00:12 The reason i'm doing these is because when i simplify those down, 4 pi over 12 is pi over 3 and 3 pi pi over 4.
00:20 These are values that are found on the unit circle.
00:23 So i would have cosine of pi over 3 times cosine of pi over 4, then that minus is going to make.
00:30 Make it a plus here, then we would do sine of pi over three times sine of pi over four.
00:36 So all this formula here is our sum and difference for cosine...
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