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September 20, 2014

September 20, 2014

Posted by **Lucy** on Saturday, August 30, 2008 at 10:10pm.

Answer: sqrt6-sqrt2/4

Thanks

- Pre-Calculus-check answers -
**Reiny**, Saturday, August 30, 2008 at 10:58pmYou might notice that 225 = 180 + 75

so sin 255 = sin(180+75)

= sin 180cos 75 + cos180sin75

= -sin75

now 75 = 45 + 30

so sin(75) = sin(45+30)

= sin45cos30 + cos45sin30

= (1/√2)(√3/2) + (1/√2)(1/2) or

= (√2/2)(√3/2) + )√2/2)(1/2)

= (√6 + √2)/4

so sin 255 = -(√6 + √2)/4

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