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Math Help - Equation For The Line Tangent To The Graph

  1. #1
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    Equation For The Line Tangent To The Graph

    Hey everyone,

    I have this question,
    “Find an equation for the line tangent to the graph y = sec x at (pi/3 , 2)”

    So far I have that,
    f(x) = sec x
    f '(x) = sec x . tan x

    I then subbed in x = (pi/3) into f '(x) to get the gradient which I found was 0, is this right?


    I wanted to make I was approaching this question correctly and if I have that just means I sub m into the equation,
    y - y1 = m(x - x1)
    and finish it off.

    Thanks!
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  2. #2
    Super Member 11rdc11's Avatar
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    Yep sounds right if all your calculations are right
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  3. #3
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    Quote Originally Posted by 11rdc11 View Post
    Yep sounds right if all you calculations are right
    Awesome, thanks ^^
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  4. #4
    Super Member 11rdc11's Avatar
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    On second check your gradient is wrong
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  5. #5
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    Quote Originally Posted by 11rdc11 View Post
    On second check your gradient is wrong
    Really? What did I do wrong.
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  6. #6
    o_O
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    f'\left(\frac{\pi}{3}\right) = \sec \left(\frac{\pi}{3}\right) \cdot \tan \left(\frac{\pi}{3}\right) = 2 \cdot \sqrt{3}
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  7. #7
    Super Member 11rdc11's Avatar
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    sec\bigg(\frac{\pi}{3}\bigg) = 2

    tan\bigg(\frac{\pi}{3}\bigg) = \sqrt{3}
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  8. #8
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    Quote Originally Posted by o_O View Post
    f'\left(\frac{\pi}{3}\right) = \sec \left(\frac{\pi}{3}\right) \cdot \tan \left(\frac{\pi}{3}\right) = 2 \cdot \sqrt{3}
    Quote Originally Posted by 11rdc11 View Post
    sec\bigg(\frac{\pi}{3}\bigg) = 2

    tan\bigg(\frac{\pi}{3}\bigg) = \sqrt{3}

    Ohhh I understand now for some reason I had that Tan pi/3 = 0

    Thanks for the help!
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