Finding the Angle of Rotation

Key Questions

  • xy term in the equation of a conic section indicates, there is a rotation of axes

  • Answer:

    Use a formula and solve for angle of rotation = thetaθ

    Explanation:

    For the formulas I use, we must put the equation in the form:

    Ax^2 +Bxy+Cy^2 +Dx + Ey +F =0Ax2+Bxy+Cy2+Dx+Ey+F=0

    Use cot2theta = (A-C)/Bcot2θ=ACB or tan2theta = B/(A-C)tan2θ=BAC.

    Solve for thetaθ.

    (The D, E, " and " FD,E, and F are not used in the formulas.)

    Your textbook/teacher may prefer a different form, which would lead to different formulas.

    Note/Example:
    If A = CA=C, then cot2theta = 0cot2θ=0, so theta = pi/4θ=π4

Questions