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    here is question
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    Name:  ds.PNG
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    where that 2 goes

    i know first to take inverse of sin sqroot 2/2
    then what to do of 2 with that?
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    (Original post by Qer)
    Name:  ds.PNG
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    where that 2 goes

    i know first to take inverse of sin sqroot 2/2
    then what to do of 2 with that?
    sin(2x) = 2 cos x sin x
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    (Original post by Zacken)
    sin(2x) = 2 cos x sin x
    can you please show me working?. it will be easier for me to understand
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    (Original post by Qer)
    can you please show me working?. it will be easier for me to understand
    No. Tell me what you've done so far. What is arcsin(sqrt(2)/2)? What is 2 times that? What is sin of that?
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    (Original post by Zacken)
    No. Tell me what you've done so far. What is arcsin(sqrt(2)/2)? What is 2 times that? What is sin of that?

    is it like that
    2 arcsin sqroot 2/2= 2 X 1/4pi = 1/2 pi
    sin( 1/2 pi)=1


    not sure that it is right?
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    (Original post by Qer)
    is it like that
    2 arcsin sqroot 2/2= 2 X 1/4pi = 1/2 pi
    sin( 1/2 pi)=1


    not sure that it is right?
    It is. See, all you had to do was try it yourself.
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    (Original post by Zacken)
    It is. See, all you had to do was try it yourself.

    can i ask some more questions?
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    (Original post by Qer)

    can i ask some more questions?
    Sure. As long as you lay out your current working/thoughts for them.
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    (Original post by Zacken)
    Sure. As long as you lay out your current working/thoughts for them.
    Name:  m.PNG
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    so
    i am ok with part a . as we can see from graph

    for part b
    i
    cos^2k =1- sin^2k
    taking sqroot
    cos k= 1- sin k

    the book shows answer is +- sqroot(1-sin^2 k)

    why they dont cancel sqroot?

    part c doesnt make any sense to me
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    (Original post by Qer)
    Name:  m.PNG
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    so
    i am ok with part a . as we can see from graph

    for part b
    i
    cos^2k =1- sin^2k
    taking sqroot
    cos k= 1- sin k

    the book shows answer is +- sqroot(1-sin^2 k)

    why they dont cancel sqroot?

    part c doesnt make any sense to me
    sqrt(1-sin^2 k) is not the same thing as 1 - sin k.

    Do you think that sqrt(1-0.5^2) = 1 - 0.5?
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    (Original post by Zacken)
    sqrt(1-sin^2 k) is not the same thing as 1 - sin k.

    Do you think that sqrt(1-0.5^2) = 1 - 0.5?
    ok
    that make sense now
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    (Original post by Qer)
    ok
    that make sense now
    You know that if 0<k<pi/2 then cos k is a positive number, which is why cos k = sqrt(1- sin^2 k)

    If -pi/2 < k < 0, what is the sign of cos k? Check a graph. Is it under/below the k-axis in that interval?
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    (Original post by Zacken)
    You know that if 0<k<pi/2 then cos k is a positive number, which is why cos k = sqrt(1- sin^2 k)

    If -pi/2 < k < 0, what is the sign of cos k? Check a graph. Is it under/below the k-axis in that interval?
    how i make graph of function cos k = sqrt(1- sin^2 k)?
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    (Original post by Qer)
    how i make graph of function cos k = sqrt(1- sin^2 k)?
    No, make a graph of the function cos k.
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    dran
    (Original post by Zacken)
    You know that if 0<k<pi/2 then cos k is a positive number, which is why cos k = sqrt(1- sin^2 k)

    If -pi/2 < k < 0, what is the sign of cos k? Check a graph. Is it under/below the k-axis in that interval?
    graph is in second quadrant ( above the axes) so it is positive
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    (Original post by Qer)
    drangraph is in second quadrant ( above the axes) so it is positive
    Right, so there's no difference to your answer. cos k = sqrt(1 - sin^2 k)

    You just need to rewrite sin^2 k in terms of x.
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    (Original post by Zacken)
    Right, so there's no difference to your answer. cos k = sqrt(1 - sin^2 k)

    You just need to rewrite sin^2 k in terms of x.
    there is also tan in par b
    is this answer for both of them?
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    (Original post by Qer)
    there is also tan in par b
    is this answer for both of them?
    You tell me. Is tan k positive for 0<k<pi/2? What about for -pi/2 < k < 0?
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    (Original post by Zacken)
    You tell me. Is tan k positive for 0<k<pi/2? What about for -pi/2 < k < 0?
    Is tan k positive for 0<k<pi/2?
    it is positive

    -pi/2 < k < 0?
    in that range it is below the axes so it is negative?
 
 
 
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