# calculus

Find the exact value of the given expression using a sum or difference formula. sin 345°

Can you help with this? I got 1/4 (squareroot 2 - square root 6)

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1. correct

Why not just check your result with a calculator?

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2. I did but it isn't one of my answer options. The options are

a. (squareroot 3 - 1) / 2 squareroot 2

b. (squareroot 3 + 1) / 2 squareroot 2

c. (- squareroot 3 + 1) / 2 squareroot 2

d. (- squareroot 3 - 1) / 2 squareroot 2

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3. poor choices for answers, they should have rationalized the answer.

That's where my hint about a calculator comes in.
Both our answers were (1/4)(√2 - √6)
if you work that out on your calculator you get
appr -.2588

working out c) you get appr -.2588
so c) is the correct choice, even though it does not look like ours

if you multiply c) by (√2/√2) , really just by 1, you get
((- √3 + 1) / 2√2 * (√2/√2)
= (-√6 + √2)/4
or
(1/4)(√2 - √6) , our answer

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