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Thread: Trig Question

  1. #1
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    Trig Question

    Can anyone please help on this.

    Don't know what I am meant to do and how to work it out.

    Thanks

    I have attached the problem.

    Trig Question-quest-9.jpg
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Braindead View Post
    Can anyone please help on this.

    Don't know what I am meant to do and how to work it out.

    Thanks

    I have attached the problem.

    Click image for larger version. 

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    note that the magnitude of the vertical side is $\displaystyle \sin \theta$ and the magnitude of the base is $\displaystyle \cos \theta$ by SOHCAHTOA.

    Now apply Pythagoras' theorem
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  3. #3
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    Thanks.

    But I don't know what the question is asking me to do.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Braindead View Post
    Thanks.

    But I don't know what the question is asking me to do.
    it is asking you to prove that $\displaystyle \sin^2 \theta + \cos^2 \theta = 1$

    just do what i said, you will get there
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  5. #5
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    Sorry I'm a bit thicker than most.

    I don't actually understand what He means by this part of the question.

    Trig Question-7.jpg

    I can understand what the first part is that sin(x)^2 + cos(x)^2 = 1

    But what is He trying to tell me to do.

    Thanks for your time.
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  6. #6
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    Quote Originally Posted by Braindead View Post
    Sorry I'm a bit thicker than most.

    I don't actually understand what He means by this part of the question.

    Click image for larger version. 

Name:	7.jpg 
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    I can understand what the first part is that sin(x)^2 + cos(x)^2 = 1

    But what is He trying to tell me to do.

    Thanks for your time.
    The triangle you have been given can only be constructed if the angle $\displaystyle \theta$ is between 0 and 90 degrees.

    Call the length of the horizontal "leg" of the triangle a. Call the length of the vertical "leg" of the triangle b. In terms of the angle $\displaystyle \theta$, what are the values for a and b?

    Once you have that, notice that you have a right triangle. Apply the Pythagorean Theorem.

    -Dan
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  7. #7
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    Quote Originally Posted by Braindead View Post
    Sorry I'm a bit thicker than most.

    I don't actually understand what He means by this part of the question.

    Click image for larger version. 

Name:	7.jpg 
Views:	41 
Size:	2.4 KB 
ID:	4076

    I can understand what the first part is that sin(x)^2 + cos(x)^2 = 1

    But what is He trying to tell me to do.

    Thanks for your time.
    He means for any angle theta between 0 degree and 90 degrees.
    0 and 90 degrees are not included because with theta as zero degree or 90 degrees, you have no right triangle. There is already one 90-degree angle in the shown right triangle. The 3 interior angles are supposed to add up only to 180 degrees.

    To picture the 0deg < theta < 90deg more, first make the theta in the figure approximately or about 5 degrees only, or 10 degrees, or dependending on how small it can get in your sketch.
    The resulting triangle looks very flat, yet, still it is a right triangle and
    sin^2(5deg) +cos^2(5deg) = 1 still.

    Then make theta about 80 degrees. The resulting right triangle looks like a a tall pole. Yet, still, sin^2(80deg) +cos^2(80deg) = 1.

    Get your calculator and check those.
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  8. #8
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    Thanks to all of you. I worked it out finally. I wish I had $1.00 for every hour I spent on it.

    Thanks a lot.
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