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Jamierox4ev3r

  • one year ago

Find the exact value of:

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  1. Jamierox4ev3r
    • one year ago
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    \(\Large\cos (-\frac{5\pi}{4})\)

  2. Jamierox4ev3r
    • one year ago
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    the negative sign is throwing me off

  3. zzr0ck3r
    • one year ago
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    \(\cos(-x)=\cos(x)\)

  4. Jamierox4ev3r
    • one year ago
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    wait. so is it basically just saying \(\Large\cos (\frac{5\pi}{4})\) o-o

  5. zzr0ck3r
    • one year ago
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    correct

  6. matlee
    • one year ago
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    \[-\frac{ 1 }{ \sqrt{2} }\]

  7. zzr0ck3r
    • one year ago
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    @matlee we all know how to use a calculator.

  8. matlee
    • one year ago
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    your smart , i hope you do

  9. zzr0ck3r
    • one year ago
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    read the rules, if you can

  10. anonymous
    • one year ago
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  11. bradely
    • one year ago
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    cos(-5pi/4) = cos(5pi/4) =cos(2pi -3pi/4) =cos(3pi/4) =cos(pi-pi/4) =-cospi/4 =-1/sqrt(2) Source: mathskey.com

  12. Jamierox4ev3r
    • one year ago
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    @matlee and @bradely , please don't provide direct answers, I don't care what the source is. So from what i see, \(\Large\cos (-\frac{5\pi}{4}) = -\frac{\sqrt{2}}{2}\)

  13. Jamierox4ev3r
    • one year ago
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    So what was the purpose of putting a negative sign in there? Just to throw of poor unsuspecting students? Or is there actually something I need to do about the said negative sign?

  14. Jamierox4ev3r
    • one year ago
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    @Nnesha @zzr0ck3r

  15. Jamierox4ev3r
    • one year ago
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    and @satellite73 thank you for the trig cheat sheet, lot of helpful things on there

  16. Nnesha
    • one year ago
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    cos is even function cos(-x)= cos(x) but careful sin and tan sin(-x)=-sin(X) odd tan(-x)=-tan(x)odd

  17. Nnesha
    • one year ago
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    about*

  18. Nnesha
    • one year ago
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    so if cos (-x)= cos(x) then sec(-x)= ?

  19. Jamierox4ev3r
    • one year ago
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    then sec(-x) would be sec(x), since sec is just the inverse function of cos

  20. Nnesha
    • one year ago
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    so -cos(-x)= ?

  21. Jamierox4ev3r
    • one year ago
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    -cos(-x)= -cos(x)

  22. Nnesha
    • one year ago
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    yep! there is an identity to prove cos(-x)=cos(x) you'll learn n calc one i guess

  23. Jamierox4ev3r
    • one year ago
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    funnnn

  24. Nnesha
    • one year ago
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    ye!

  25. Jamierox4ev3r
    • one year ago
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    XD Thank you

  26. Nnesha
    • one year ago
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    np :=)

  27. zzr0ck3r
    • one year ago
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    cos gives you the \(x\) value on the angle, |dw:1441072239511:dw| The bottom angle is the negative version of the top angle, but they both give the same x values.

  28. zzr0ck3r
    • one year ago
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    I hope that makes sense.

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