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The points A, B and C lie on a circle with centre O, as shown in the diagram - HSC - SSCE Mathematics Extension 1 - Question 12 - 2017 - Paper 1

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The points A, B and C lie on a circle with centre O, as shown in the diagram. The size of \( \angle ZAOC \) is 100°. Find the size of \( \angle ZABC \), giving reas... show full transcript

Worked Solution & Example Answer:The points A, B and C lie on a circle with centre O, as shown in the diagram - HSC - SSCE Mathematics Extension 1 - Question 12 - 2017 - Paper 1

Step 1

Find the size of \( \angle ZABC \), giving reasons.

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Answer

To find the angle ( \angle ZABC ), we can use the property that the angle at the circumference is half the angle at the center when both angles subtend the same arc.

Given that ( \angle ZOAC = 100° ), we first find the reflex angle ( \angle ZAO = 360° - 100° = 260° ).

Using the relationship:

ABC=12reflex ZAO=12(260°)=130°.\angle ABC = \frac{1}{2} \text{reflex } \angle ZAO = \frac{1}{2} (260°) = 130°.

Therefore, ( \angle ZABC = 130° ).

Step 2

Carefully sketch the graphs of \( y = |x + 1| \) and \( y = 3 - |x - 2| \) on the same axes, showing all intercepts.

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Answer

  1. The graph of ( y = |x + 1| ) will have a V-shape with the vertex at ( (-1,0) ).
  2. The graph of ( y = 3 - |x - 2| ) will also have a V-shape with the vertex at ( (2, 3) ) and intercepts at ( (1, 2) ) and ( (3, 0) ).
  3. Ensure the x-values are clearly marked and the y-intercepts are labeled correctly.

Step 3

Using the graphs from part (i), or otherwise, find the range of values of \( x \) for which \( |x + 1| + |x - 2| = 3. \)

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Answer

To find the range, we solve the equation:

  1. For ( x < -1 ): ( -(x + 1) + (2 - x) = 3 ) leads to no solution.
  2. For ( -1 \leq x < 2 ): ( (x + 1) + (2 - x) = 3 ), leads to the range ( x = -1 ).
  3. For ( x \geq 2 ): ( (x + 1) + (x - 2) = 3 ) translates to ( 2x - 1 = 3 ), yielding ( x = 2 ).

Thus, the range of ( x ) is ( -1 \leq x ext{ or } x = 2. )

Step 4

Show that \( h \) satisfies the equation \( 3h^3 - 9h + 2 = 0. \)

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Answer

To demonstrate this,

  1. The volume of the first solid formed by the semicircle is given by: V1=π0h(1x2)2dx=π0h(1x2)dx=π[xx33]0h=π(hh33).V_1 = \pi \int_0^h (\sqrt{1-x^2})^2 dx = \pi \int_0^h (1-x^2) dx = \pi \left[ x - \frac{x^3}{3} \right]_0^h = \pi \left( h - \frac{h^3}{3} \right).
  2. The volume of the second solid formed by the remaining area is: V2=πh1(1x2)2dx=π(π2V1).V_2 = \pi \int_h^1 (\sqrt{1-x^2})^2 dx = \pi \left( \frac{\pi}{2} - V_1 \right).
  3. Setting the volumes ratio to 2:1 will lead to: V1V2=12ultimately giving the equation 3h39h+2=0.\frac{V_1}{V_2} = \frac{1}{2} \Rightarrow \text{ultimately giving the equation } 3h^3 - 9h + 2 = 0.

Step 5

Given \( h_1 = 0 \) as the first approximation for \( h \), use one application of Newton's method to find a second approximation for \( h. \)

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Answer

To apply Newton's method:

  1. Compute the function: f(h)=3h39h+2f(h) = 3h^3 - 9h + 2 with ( f(0) = 2. )
  2. Find the derivative: f(h)=9h29.f'(h) = 9h^2 - 9.
  3. Calculate: h2=h1f(h1)f(h1)=029=29.h_2 = h_1 - \frac{f(h_1)}{f'(h_1)} = 0 - \frac{2}{-9} = \frac{2}{9}.
  4. Therefore, the approximation for ( h ) would be rendered as ( h_2 = \frac{2}{9}. )

Step 6

Find the acceleration of the particle as a function of t.

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Answer

To find the acceleration, we first differentiate the displacement with respect to time:

  1. ( x = 4 - e^{-2t} )
  2. Taking the first derivative: dxdt=2e2t\frac{dx}{dt} = 2e^{-2t}
  3. The acceleration, which is the second derivative: d2xdt2=4e2t.\frac{d^2x}{dt^2} = -4e^{-2t}. \nHence, the acceleration of the particle as a function of ( t ) is given by ( -4e^{-2t}. )

Step 7

Evaluate \( \lim_{x \to 0} \frac{1 - \cos 2\pi x}{x^2}. \)

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Answer

To evaluate this limit, we can use the substitution:

  1. We know that as ( x \to 0 ), ( 1 - \cos(2\pi x) \approx \frac{(2\pi x)^2}{2} ) using the Taylor series expansion.
  2. Therefore: limx01cos2πxx2=limx02π2x22x2=π2.\lim_{x \to 0} \frac{1 - \cos 2\pi x}{x^2} = \lim_{x \to 0} \frac{2\pi^2x^2}{2x^2} = \pi^2.
  3. Thus, the limit evaluates to ( \pi^2. )

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