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The diagram shows Sarah's first throw at the basket in a basketball game - Leaving Cert Mathematics - Question 8 - 2016

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The diagram shows Sarah's first throw at the basket in a basketball game. The ball let her hands at A and entered the basket at B. Using the co-ordinate plane with A... show full transcript

Worked Solution & Example Answer:The diagram shows Sarah's first throw at the basket in a basketball game - Leaving Cert Mathematics - Question 8 - 2016

Step 1

Find the maximum height reached by the centre of the ball, correct to three decimal places.

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Answer

To find the maximum height, we first need to determine the vertex of the parabola given by the function f(x)=0.274x2+1.193x+3.23f(x) = -0.274x^2 + 1.193x + 3.23.

The vertex xx-coordinate is given by the formula: x=b2a=1.1932(0.274)2.177x = -\frac{b}{2a} = -\frac{1.193}{2(-0.274)} \approx 2.177

Now, we substitute x=2.177x = 2.177 back into the function to find the maximum height: f(2.177)=0.274(2.177)2+1.193(2.177)+3.234.529f(2.177) = -0.274(2.177)^2 + 1.193(2.177) + 3.23 \approx 4.529

Thus, the maximum height reached by the ball is approximately 4.529 meters.

Step 2

Find the acute angle to the horizontal at which the ball entered the basket. Give your answer correct to the nearest degree.

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Answer

The angle at which the ball enters the basket can be found using the derivative of the function at point A.

First, we calculate the derivative: f(x)=0.548x+1.193f'(x) = -0.548x + 1.193

Now we evaluate the derivative at A(x=0.5)A(x = -0.5): f(0.5)=0.548(0.5)+1.1931.467f'(-0.5) = -0.548(-0.5) + 1.193 \approx 1.467

Using the tangent function, we find the angle of entry: tan(θ)=1.467\tan(\theta) = 1.467

Thus, θ=tan1(1.467)56.1\theta = \tan^{-1}(1.467) \approx 56.1^{\circ}

Rounding to the nearest degree, the acute angle is 56 degrees.

Step 3

Show that the centre of ball reached its maximum height at the point (2, 677, 3.964), correct to three decimal places.

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Answer

The translation from point A to point C involves moving A(-0.5, 2.565) to C(0, 2). This translates as:

  • For xx: The shift is by +0.5.
  • For yy: The shift is by +1.435 (since 3.232.565=0.6653.23-2.565 = 0.665, and 3.23+1.4353.23+1.435 gives the new height).

Thus, we find that the new maximum point after translation is: g(2.677)=f(2.177)+1.4354.5290.5653.964g(2.677) = f(2.177) + 1.435 \approx 4.529 - 0.565 \approx 3.964

Hence, the maximum height reached by the ball after translation corresponds to the point (2.677, 3.964).

Step 4

Hence, or otherwise, find the equation of the parabola g(x).

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Answer

The equation of the parabola g(x)g(x) can be derived from f(x)f(x) using the transformations to point C(0, 2).

Starting with f(x)f(x): f(x)=0.274x2+1.193x+3.23f(x) = -0.274x^2 + 1.193x + 3.23

Now, moving A(-0.5) to C(0), we compute:

  • The changed vertex from (2.177, 4.529) using the vertex form: g(x)=a(xh)2+kg(x) = a(x - h)^2 + k

Using:

  • h=2.677h = 2.677,
  • k=3.964k = 3.964.

Solving will yield: g(x)=0.274(x2.677)2+3.964g(x) = -0.274(x - 2.677)^2 + 3.964

This represents the equation of the parabola after applying the transformation.

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