If the line 3x−2y+12=03x - 2y + 12 = 0 intersects the parabola 4y=3x24y = 3x^2 at the points AA and BB, then at the vertex of the parabola, the line segment ABAB subtends an angle equal to

Answer: The angle subtended by the line segment ABAB at the vertex of the parabola is tan⁡−1(97)\tan^{-1}\left(\frac{9}{7}\right).

Step-by-step solution

Step 1: Find the intersection points A and B

First, we need to find the coordinates of the intersection points A and B. We can do this by substituting the expression for yy from the linear equation into the parabolic equation. The line equation is 3x−2y+12=03x - 2y + 12 = 0, which can be rewritten as y=3x+122y = \frac{3x + 12}{2}. Substitute this into the parabola equation 4y=3x24y = 3x^2.

Step 2: Solve the quadratic equation for x

Simplify the equation to get a quadratic equation in terms of xx. After simplifying, we get 3x2−6x−24=03x^2 - 6x - 24 = 0, which can be further simplified to x2−2x−8=0x^2 - 2x - 8 = 0. Factoring this quadratic equation gives us (x−4)(x+2)=0(x - 4)(x + 2) = 0, yielding xx -values of 44 and −2-2.

Step 3: Find the coordinates of A and B

Now, substitute these xx -values back into the linear equation y=3x+122y = \frac{3x + 12}{2} to find the corresponding yy -values. For x=4x=4, y=12y=12, so point A is (4,12)(4, 12). For x=−2x=-2, y=3y=3, so point B is (−2,3)(-2, 3).

Step 4: Identify the vertex of the parabola

The equation of the parabola is 4y=3x24y = 3x^2, which can be written as y=34x2y = \frac{3}{4}x^2. This is a parabola of the form y=ax2y = ax^2, which has its vertex at the origin (0,0)(0, 0). Let's call the vertex V(0,0)V(0, 0).

Step 5: Calculate the slopes of VA and VB

To find the angle subtended by the line segment AB at the vertex V, we need to find the slopes of the lines VA and VB. The slope of VA is 12−04−0=3\frac{12-0}{4-0} = 3. The slope of VB is 3−0−2−0=−32\frac{3-0}{-2-0} = -\frac{3}{2}.

Step 6: Calculate the angle using the tangent formula

The angle θ\theta between two lines with slopes m1m_1 and m2m_2 is given by the formula tan⁡θ=∣m1−m21+m1m2∣\tan \theta = \left|\frac{m_1 - m_2}{1 + m_1 m_2}\right|. Substituting the slopes mVA=3m_{VA} = 3 and mVB=−32m_{VB} = -\frac{3}{2}, we get tan⁡θ=97\tan \theta = \frac{9}{7}. Therefore, the angle θ\theta is tan⁡−1(97)\tan^{-1}\left(\frac{9}{7}\right).

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