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Show that, for small values of x, the graph of y = 5 + 4 \\sin \left( \frac{x}{2} \right) + 12 \tan \left( \frac{x}{3} \right) can be approximated by a straight line. - AQA - A-Level Maths Mechanics - Question 5 - 2018 - Paper 3

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Show-that,-for-small-values-of-x,-the-graph-of---y-=-5-+-4-\\sin-\left(-\frac{x}{2}-\right)-+-12-\tan-\left(-\frac{x}{3}-\right)-can-be-approximated-by-a-straight-line.-AQA-A-Level Maths Mechanics-Question 5-2018-Paper 3.png

Show that, for small values of x, the graph of y = 5 + 4 \\sin \left( \frac{x}{2} \right) + 12 \tan \left( \frac{x}{3} \right) can be approximated by a straight li... show full transcript

Worked Solution & Example Answer:Show that, for small values of x, the graph of y = 5 + 4 \\sin \left( \frac{x}{2} \right) + 12 \tan \left( \frac{x}{3} \right) can be approximated by a straight line. - AQA - A-Level Maths Mechanics - Question 5 - 2018 - Paper 3

Step 1

Use small angle approximation for sin x or tan x

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Answer

For small values of x, we can use the approximations:

  • ( \sin(x) \approx x )
  • ( \tan(x) \approx x )

Thus, we have:

[ \sin \left( \frac{x}{2} \right) \approx \frac{x}{2} ]
[ \tan \left( \frac{x}{3} \right) \approx \frac{x}{3} ]

Step 2

Substitute approximations into the equation

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Answer

Substituting these approximations into the original equation:

[ y = 5 + 4 \cdot \frac{x}{2} + 12 \cdot \frac{x}{3} ]

This simplifies to:

[ y = 5 + 2x + 4x ]

Thus:

[ y = 5 + 6x ]

Step 3

Conclude that the graph can be approximated by a straight line

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Answer

The resulting equation is:

[ y = 6x + 5 ]

This represents a straight line with a slope of 6 and a y-intercept of 5. Therefore, we can conclude that for small values of x, the graph can indeed be approximated by a straight line.

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