Solved on Nov 18, 2023

Rewrite rotation formulas to eliminate xyx'y'-term in equation x2+16xy+y23=0x^2 + 16xy + y^2 - 3 = 0.

STEP 1

Assumptions1. The given equation is x+16xy+y3=0x^{}+16 x y+y^{}-3=0 . We want to eliminate the xyx'y' term in the rotated system.

STEP 2

In a rotated coordinate system, the coordinates (x,y)(x, y) can be transformed to (x,y)(x', y') using the rotation formulasx=xcos(θ)ysin(θ)x = x' \cos(\theta) - y' \sin(\theta)y=xsin(θ)+ycos(θ)y = x' \sin(\theta) + y' \cos(\theta)where θ\theta is the angle of rotation.

STEP 3

Substitute the rotation formulas into the given equationx2+16xy+y23=0x^{2}+16 x y+y^{2}-3=0to get(xcos(θ)ysin(θ))2+16(xcos(θ)ysin(θ))(xsin(θ)+ycos(θ))+(xsin(θ)+ycos(θ))23=0(x' \cos(\theta) - y' \sin(\theta))^2 +16(x' \cos(\theta) - y' \sin(\theta))(x' \sin(\theta) + y' \cos(\theta)) + (x' \sin(\theta) + y' \cos(\theta))^2 -3 =0

STEP 4

We want to eliminate the xyx'y' term in the rotated system. This will happen when the coefficient of xyx'y' in the expanded equation is zero.The coefficient of xyx'y' is obtained by multiplying the coefficients of xyx' y' in the terms x2x'^2, xyx'y', and y2y'^2.
In the expanded equation, the coefficient of xyx'y' is 16cos(θ)sin(θ)2sin(θ)cos(θ)16\cos(\theta)\sin(\theta) -2\sin(\theta)\cos(\theta).

STEP 5

Set the coefficient of xyx'y' to zero and solve for θ\theta16cos(θ)sin(θ)2sin(θ)cos(θ)=016\cos(\theta)\sin(\theta) -2\sin(\theta)\cos(\theta) =0

STEP 6

Factor out sin(θ)cos(θ)\sin(\theta)\cos(\theta) to simplify the equationsin(θ)cos(θ)(162)=0\sin(\theta)\cos(\theta)(16 -2) =0

STEP 7

olve for θ\thetasin(θ)cos(θ)=0\sin(\theta)\cos(\theta) =0This equation is satisfied when θ=0,π2,π,3π2\theta =0, \frac{\pi}{2}, \pi, \frac{3\pi}{2}.

STEP 8

However, a rotation by 00 or π\pi radians would not change the system, and a rotation by π2\frac{\pi}{2} or 3π2\frac{3\pi}{2} radians would merely swap the xx and yy axes. Therefore, none of these solutions eliminate the xyx'y' term.

STEP 9

The problem lies in the fact that we have a term with xyx'y' in the equation, which cannot be eliminated by a simple rotation. This is because the given equation represents a hyperbola, which always has an xyx'y' term in its general form.

STEP 10

To eliminate the xyx'y' term, we need to rotate the axes by an angle θ\theta such that the axes align with the symmetry axes of the hyperbola. This angle θ\theta can be found by calculating the angle of the lines of symmetry of the hyperbola.

STEP 11

The angle θ\theta is given by\theta = \frac{}{} \arctan\left(\frac{ab}{a^ - b^}\right)where aa and bb are the coefficients of x^ and y^ respectively.

STEP 12

Substitute a=a = and b=b = into the formula to calculate θ\thetaθ=2arctan(2()()22)\theta = \frac{}{2} \arctan\left(\frac{2()()}{^2 -^2}\right)

STEP 13

implify the equation to find θ\thetaθ=2arctan()\theta = \frac{}{2} \arctan(\infty)

STEP 14

The arctan()\arctan(\infty) is π2\frac{\pi}{2}, soθ=2π2=π4\theta = \frac{}{2} \cdot \frac{\pi}{2} = \frac{\pi}{4}

STEP 15

Therefore, a rotation of π4\frac{\pi}{4} radians (or45 degrees) will align the axes with the symmetry axes of the hyperbola and eliminate the xyx'y' term.
The rotation formulas that will transform the given equation into a form without an xyx'y' term arex=xcos(π4)ysin(π4)x' = x \cos\left(\frac{\pi}{4}\right) - y \sin\left(\frac{\pi}{4}\right)y=xsin(π4)+ycos(π4)y' = x \sin\left(\frac{\pi}{4}\right) + y \cos\left(\frac{\pi}{4}\right)

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