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anonymous

  • 5 years ago

what is the exact value of sin15 ? (using the subtraction formula)

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  1. anonymous
    • 5 years ago
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    help!

  2. anonymous
    • 5 years ago
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    I don't know about the subtraction formula (never heard of it) but the half angle identity should work

  3. nikvist
    • 5 years ago
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    \[\sin^215=\frac{1-\cos 30}{2}=\frac{1-\sqrt{3}/2}{2}=\frac{2-\sqrt{3}}{4}\] \[\sin15=\frac{\sqrt{2-\sqrt{3}}}{2}\]

  4. anonymous
    • 5 years ago
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    That's it right there^

  5. anonymous
    • 5 years ago
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    I think the subtraction formula would mean that you would take two sin values that you know and use them to get sin 15 Sin 45 - Sin 30 I will get back with the formula

  6. anonymous
    • 5 years ago
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    OK here is the formula sin(A−B) = sin A cos B − cos A sin B

  7. anonymous
    • 5 years ago
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    im required to use this formula sin(s-t)= sin(s)cos(t) - cos(s)sin(t)

  8. anonymous
    • 5 years ago
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    Sin(45-30) = sin45*cos30 - cos45*sin30

  9. anonymous
    • 5 years ago
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    Sin 45 = sqrt2/2 cos 45 = sqrt2/2 sin 30 = 1/2 cos 30 = sqrt3/2

  10. anonymous
    • 5 years ago
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    The difference identity! Yup that works better!

  11. anonymous
    • 5 years ago
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    sqrt2/2*sqrt3/2 - sqrt2/2*1/2 sqrt6/2 - sqrt2/2 (sqrt6 - sqrt2) /2

  12. anonymous
    • 5 years ago
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    would it be over 4 after multiplying

  13. anonymous
    • 5 years ago
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    OOPS - yes

  14. anonymous
    • 5 years ago
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    thanks so much!

  15. anonymous
    • 5 years ago
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    U R Welcome

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