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Solve trigonometric equation

  1. Oct 9, 2011 #1
    I wolud like to solve the folowing equation:
    A*cos(B*t)+sin(B*t)*(C-t)-D=0 (t is unknown)
    It is urgent.
    Thanks in advance.
  2. jcsd
  3. Oct 9, 2011 #2

    Char. Limit

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    Gold Member

    Unless you have specific numerical values for at least some of the constants A, B, C, and D, this isn't solvable for t. Sorry.
  4. Oct 9, 2011 #3
    Huh... is it possible to make an approxiamtion?

    I would like to calculate the intersection between a sine function and a linear function. A sine function is of a form: y=A*sin(x). A linear function intersects sine function in two points. The first one (P1(pi,0)) is known, but we do not know the other one. We know an area between the x axis and the sine + linear functios (look at the sketch). After integration we get an equation form the first post.
  5. Oct 9, 2011 #4

    Char. Limit

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    Gold Member

    Well you have a problem here, then, because a linear function CAN'T intersect a sine function in exactly two points.
  6. Oct 9, 2011 #5
    Yes, they intersect in 3 points, but the third point is not important for me. I am not sure if you can see the sketch, I am sure I attached it, but I cannot see it.

    Attached Files:

  7. Oct 15, 2011 #6
    You have not specified the linear equation
    So lets take a simple example

    y=0.5 intersecting y=sin x
    So we have
    sin x = 0.5
    Take the arcsine of both sides.
    x = arcsine 0.5
    Which yields pi/6 and 5pi/6 for 0 < x < 2pi

    Similar approach should work for any linear equation y = mx + b

    Edit in;
    Looking at your equation above, you may not be able to solve it
    algebraically. You may need to do it numerically.
    A graphing calculator will be a big help.
    It simply pick hundreds of values for t and calculates what that
    gives for the equation and locates where the value is zero.
    Just brute force math.
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