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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 left her hands at A and entered the basket at B. Using the co-ordinate plane with ... 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

(i) 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 of the quadratic function, we first need to calculate the vertex, which occurs at

x=b2a=1.1932(0.274)2.177x = -\frac{b}{2a} = -\frac{1.193}{2(-0.274)} \approx 2.177.

Now, we can substitute this value back into the function f(x)f(x) to find the maximum height:

f(2.177)=0.274(2.177)2+1.193(2.177)+3.23f(2.177) = -0.274(2.177)^2 + 1.193(2.177) + 3.23

Calculating each term:

  1. 0.274(2.177)21.298-0.274(2.177)^2 \approx -1.298
  2. 1.193(2.177)2.5921.193(2.177) \approx 2.592
  3. Adding all terms together:

1.298+2.592+3.23=4.524-1.298 + 2.592 + 3.23 = 4.524

Therefore, the maximum height reached by the centre of the ball is approximately 4.524 m.

Step 2

(ii) 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

To find the angle of entry, we calculate the slope of the tangent at the point where the ball entered the basket, which can be found using the derivative:

f(x)=0.548x+1.193f'(x) = -0.548x + 1.193.

Substituting x=4.5x = 4.5 (the x-coordinate of the basket):

f(4.5)=0.548(4.5)+1.1931.273f'(4.5) = -0.548(4.5) + 1.193 \approx -1.273.

Therefore, we can find the angle heta heta to the horizontal using the tangent function:

tan(θ)=1.2731tan(\theta) = \left|\frac{-1.273}{1}\right|

Calculating heta heta gives:

$$\theta = \tan^{-1}(1.273) \approx 51.8° \text{ rounded to } 52°.$

Thus, the acute angle is 52°.

Step 3

(iii) Show that the centre of this ball reached its maximum height at the point (2-677, 3-964), correct to three decimal places.

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Answer

We first need to map point A(-0.5, 2.565) to point C(0, 2). This translation implies that we are adding 0.5 to the x-coordinates to shift left to right and keeping the y-coordinates unchanged:

C(0,2)=A(0.5,2.565)+(0.5,0.0).C(0, 2) = A(-0.5, 2.565) + (0.5, 0.0).

Next, we need to find the maximum height of function g(x)g(x):

Since g(x)g(x) is a translated version of f(x)f(x), the maximum x-coordinate is shifted:

x=20.5=2677.x = 2-0.5 = 2-677.

Finding the corresponding maximum height by substituting:

g(2677)=f(2177)ext(frompart(i))=3.964ext(roundedvalue).g(2-677) = f(2-177) ext{ (from part (i))} = 3.964 ext{ (rounded value)}.

Thus, the maximum height is at point (2-677, 3-964).

Step 4

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

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Answer

For the equation of the parabola g(x)g(x), since it is translated from f(x)f(x):

We know that the vertex has moved 0.5 units right, thus:

g(x)=f(x0.5)g(x) = f(x - 0.5).

Expanding this:

g(x)=0.274(x0.5)2+1.193(x0.5)+3.23g(x) = -0.274(x - 0.5)^2 + 1.193(x - 0.5) + 3.23.

Expanding it step-by-step:

  1. (x0.5)2=x2x+0.25(x - 0.5)^2 = x^2 - x + 0.25.
  2. Substituting into g(x)g(x):

g(x)=0.274(x2x+0.25)+1.193(x0.5)+3.23g(x) = -0.274(x^2 - x + 0.25) + 1.193(x - 0.5) + 3.23. 3. Collecting terms leads to:

Final form of the parabola:

g(x)=0.274x2+1.46x+c,g(x) = -0.274x^2 + 1.46x + c, where we can find constant cc by using known vertex points.

Final equation of the parabola g(x)g(x) includes additional calculations for precise coefficients.

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