Question

Identify the graph of the equation. What is the angle of rotation for the equation? (Picture provided)

Answer 1

Answer:

The equation is that of ellipse withe angle of rotation 30° ⇒ answer (d)

Step-by-step explanation:

* Lets talk about the general form of the conic equations

- Ax² + Bxy + Cy² +D = 0 (center is the origin)

- A is the coefficient of x² , B is the coefficient of xy

 C is the coefficient of y² , D is the numerical term

* Now we will study how to know the type of the graph of this equation

- If A and C have different signs (different values)

∴ The equation is that of an ellipse

- If A and C have different signs (different values)

∴ The equation is on a hyperbola

* Now look at the equation:

 13x² + 6√3 xy + 7y² - 16 = 0

∵ A = 13 , B = 6√3 , C = 7 , D = -16

∵ A and C have same sign

∴ The equation is that of an ellipse

* Now lets find the angle of rotation by using the Rule:

- tan(2Ф) = B/(A - C) ⇒ Ф is the angle of rotation

- By using the value of A , B and C

∴ tan(2Ф) = 6√3/(13 - 7) = 6√3/6 = √3

∴ 2Ф = $tan^{-1}\sqrt{3}=60$

∴ 2Ф = 60° ⇒ divide both sides by 2

∴ Ф = 30°

∴ The angle of rotation is 30°

∴ The equation is that of ellipse withe angle of rotation 30°

* The graph represent the ellipse

- The purple line represents the angle of rotation