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3 (12 marks) Use a SEPARATE writing booklet - HSC - SSCE Mathematics Extension 1 - Question 3 - 2004 - Paper 1

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3 (12 marks) Use a SEPARATE writing booklet. (a) Find \( \int \cos 4x \, dx \) : (b) Let \( P(x) = (x + 1)(x - 3)Q(x) + a(x + 1) + b \), where \( Q(x) \) is a poly... show full transcript

Worked Solution & Example Answer:3 (12 marks) Use a SEPARATE writing booklet - HSC - SSCE Mathematics Extension 1 - Question 3 - 2004 - Paper 1

Step 1

Find \( \int \cos 4x \, dx \) :

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Answer

To find the integral, we can use the formula for the integral of cosine:

cos(kx)dx=1ksin(kx)+C\int \cos(kx) \, dx = \frac{1}{k} \sin(kx) + C

For ( k = 4 ):

cos4xdx=14sin4x+C\int \cos 4x \, dx = \frac{1}{4} \sin 4x + C

Step 2

What is the value of \( b \) ?

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Answer

To find ( b ), we can utilize the information that when ( P(x) ) is divided by ( (x + 1) ), the remainder is -11:

Substituting ( x = -1 ):

( P(-1) = (-1 + 1)(-1 - 3)Q(-1) + a(-1 + 1) + b = -11 \implies b = -11 ).

Step 3

What is the remainder when \( P(x) \) is divided by \( (x + 1)(x - 3) \) ?

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Using the Remainder Theorem, we know the remainders found from dividing by the factors:\

  • For ( (x + 1) ), remainder is -11,
  • For ( (x - 3) ), remainder is 1.

Thus, the remainder when dividing by ( (x + 1)(x - 3) ) can be expressed as: ( R(x) = Ax + B ) and substituting both conditions will help find A and B.

Step 4

Find an expression for \( x \) in terms of \( h \).

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Answer

From the relationship in the right triangle formed, we can apply Pythagoras' theorem:

x2+h2=16x^2 + h^2 = 16

Thus, solving for ( x ):

x=16h2x = \sqrt{16 - h^2}

Step 5

At what rate is the pontoon moving away from the jetty?

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Answer

Using related rates, we differentiate the expression for ( x ):

dxdt=12(16h2)12(2hdhdt)\frac{dx}{dt} = \frac{1}{2(16 - h^2)^{\frac{1}{2}}}(-2h\frac{dh}{dt})

Then substitute ( h = -1 ) and ( \frac{dh}{dt} = 0.3 \text{ m/h} ) to find ( \frac{dx}{dt} ).

Step 6

Explain why \( \angle FAC = 60^\circ \).

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Answer

The geometry of the figure indicates that triangle ( FAC ) is equilateral as all sides are equal; hence, all angles, including ( \angle FAC ), measure 60 degrees.

Step 7

Show that \( FO = \sqrt{6} \) metres.

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Answer

In the right triangle formed by the center O, point F and line segment AC:

Using the coordinates: Each edge being 2 meters, calculate the lengths:

FO=AO2+AF2=22+22=4+2=6 m.FO = \sqrt{AO^2 + AF^2} = \sqrt{2^2 + 2^2} = \sqrt{4 + 2} = \sqrt{6}\text{ m}.

Step 8

Calculate the size of \( \angle XYF \) to the nearest degree.

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Answer

Using trigonometry: The relationship between angles ensures that we can apply the tangent function:

tan(XYF)=XYFY=16\tan(\angle XYF) = \frac{XY}{FY} = \frac{1}{\sqrt{6}}

Solving gives the angle as:\n Calculate the angle using Inverse Tangent function and round to the nearest degree.

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