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mitchelsewbaran

  • 3 years ago

Find an exact value. cos 15°

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  1. mitchelsewbaran
    • 3 years ago
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  2. RadEn
    • 3 years ago
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    setting 15 = (45-30)

  3. RadEn
    • 3 years ago
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    then use the formula : cos(A-B) = cosAcosB + sinAsinB

  4. RadEn
    • 3 years ago
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    here given A=45 and B=30 degrees

  5. mitchelsewbaran
    • 3 years ago
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    cos 45cos30 +sin45cos30?

  6. RadEn
    • 3 years ago
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    45 and 30 are the special angles.. u have to remember the values of sin and cos for angles 30 and 45 degrees

  7. mitchelsewbaran
    • 3 years ago
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    ok. how do i solve from here?

  8. RadEn
    • 3 years ago
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    u just put the values of them (sin45, sin 30, cos45, cos 30)

  9. RadEn
    • 3 years ago
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    cos 45cos30 +sin45cos30 = ... (calculate it and simply)

  10. mitchelsewbaran
    • 3 years ago
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    i got this

  11. RadEn
    • 3 years ago
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    hmm.. what identity did u use ? it should be : cos 45cos30 +sin45cos30 do u know the exactly value of sin30 ? sin45 ? cos30 ? cos45 ?

  12. miley28
    • 3 years ago
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    just put the values cos45 =1/root 2 and cos 30= root3/2

  13. miley28
    • 3 years ago
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    sin 45=1/root ovr2 and sin 30=1/2...the multiply and add

  14. mitchelsewbaran
    • 3 years ago
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    1/root ovr2 or 1/ root 2?

  15. miley28
    • 3 years ago
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    its the same thing...

  16. mitchelsewbaran
    • 3 years ago
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    o

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