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Complete the table below, giving the values of y to 2 decimal places - Edexcel - A-Level Maths Pure - Question 5 - 2009 - Paper 2

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Complete the table below, giving the values of y to 2 decimal places. $x$ | 1 | 1.4 | 1.8 | 2.2 | 2.6 | 3 ---|---|---|---|---|---|--- $y$ | 3 | 3.47 | | | | 4... show full transcript

Worked Solution & Example Answer:Complete the table below, giving the values of y to 2 decimal places - Edexcel - A-Level Maths Pure - Question 5 - 2009 - Paper 2

Step 1

Complete the table below, giving the values of y to 2 decimal places.

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Answer

To find the values of y for given x, we will use the equation:
y=10xx2.y = \sqrt{10x - x^{2}}.

Calculating each value:

  • For x=1x = 1:
    y=10112=9=3.00y = \sqrt{10 \cdot 1 - 1^{2}} = \sqrt{9} = 3.00
  • For x=1.4x = 1.4: y=101.4(1.4)2=141.96=12.043.47y = \sqrt{10 \cdot 1.4 - (1.4)^{2}} = \sqrt{14 - 1.96} = \sqrt{12.04} \approx 3.47
  • For x=1.8x = 1.8: y=101.8(1.8)2=183.24=14.763.84y = \sqrt{10 \cdot 1.8 - (1.8)^{2}} = \sqrt{18 - 3.24} = \sqrt{14.76} \approx 3.84
  • For x=2.2x = 2.2: y=102.2(2.2)2=224.84=17.164.14y = \sqrt{10 \cdot 2.2 - (2.2)^{2}} = \sqrt{22 - 4.84} = \sqrt{17.16} \approx 4.14
  • For x=2.6x = 2.6: y=102.6(2.6)2=266.76=19.244.39y = \sqrt{10 \cdot 2.6 - (2.6)^{2}} = \sqrt{26 - 6.76} = \sqrt{19.24} \approx 4.39
  • For x=3x = 3:
    y=10332=309=214.58y = \sqrt{10 \cdot 3 - 3^{2}} = \sqrt{30 - 9} = \sqrt{21} \approx 4.58

Thus, the completed table is:

xx11.41.82.22.63
yy3.003.473.844.144.394.58

Step 2

Use the trapezium rule, with all the values of y from your table, to find an approximation for the value of \( \int_{1}^{3} \sqrt{10x - x^{2}} \, dx \).

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Answer

The trapezium rule formula for approximating the integral is given by:

abf(x)dxh2(f(x0)+2f(x1)+2f(x2)++2f(xn1)+f(xn))\int_{a}^{b} f(x) \, dx \approx \frac{h}{2} \left( f(x_{0}) + 2f(x_{1}) + 2f(x_{2}) + \ldots + 2f(x_{n-1}) + f(x_{n}) \right)

where:

  • h=banh = \frac{b-a}{n}
  • f(xi)f(x_{i}) are values of the function at the corresponding xix_{i} values.

In our case, a=1a = 1, b=3b = 3, and (n=5)(n = 5) so:

h=315=0.4h = \frac{3 - 1}{5} = 0.4

The values of y from the completed table are:

  • f(1)=3.00f(1) = 3.00
  • f(1.4)=3.47f(1.4) = 3.47
  • f(1.8)=3.84f(1.8) = 3.84
  • f(2.2)=4.14f(2.2) = 4.14
  • f(2.6)=4.39f(2.6) = 4.39
  • f(3)=4.58f(3) = 4.58

Thus, substituting in the trapezium rule:

1310xx2dx0.42(3.00+23.47+23.84+24.14+24.39+4.58)\int_{1}^{3} \sqrt{10x - x^{2}} \, dx \approx \frac{0.4}{2} \left( 3.00 + 2 \cdot 3.47 + 2 \cdot 3.84 + 2 \cdot 4.14 + 2 \cdot 4.39 + 4.58 \right)

Calculating this gives:

0.2(3.00+6.94+7.68+8.28+8.78+4.58)\approx 0.2 \left( 3.00 + 6.94 + 7.68 + 8.28 + 8.78 + 4.58 \right) =0.239.26=7.852= 0.2 \cdot 39.26 = 7.852

Therefore, the approximation for the integral is approximately 7.85.

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