From a point A due south of a tower, the angle of elevation of the top of the tower T is 23° - HSC - SSCE Mathematics Extension 1 - Question 6 - 2008 - Paper 1
Question 6
From a point A due south of a tower, the angle of elevation of the top of the tower T is 23°. From another point B, on a bearing of 120° from the tower, the angle of... show full transcript
Worked Solution & Example Answer:From a point A due south of a tower, the angle of elevation of the top of the tower T is 23° - HSC - SSCE Mathematics Extension 1 - Question 6 - 2008 - Paper 1
Step 1
Copy or trace the diagram into your writing booklet, adding the given information to your diagram.
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Answer
Draw the tower with point A directly south of it, making sure to label the angles and distances accurately. Point B should be connected with angle T's respective elevation of 32° from the bearing of 120°.
Step 2
Hence find the height of the tower.
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Answer
From point A, we can use the tangent of angle 23° to find the height (h) of the tower:
h=AB×tan(23°)
Calculate the height using the distance AB (200 m):
h=200×tan(23°)≈200×0.4245≈84.9extm.
Therefore, the height of the tower is approximately 84.9 metres.
Step 3
Use this result to solve sin 3θ + sin 2θ = sin θ for 0 ≤ θ ≤ 2π.
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Answer
Utilize the equation sin 3θ = 3 sin θ - 4 sin³ θ:
Substitute into the equation, giving:
3sinθ−4sin3θ+sin2θ−sinθ=0
Rearranging yields:
−4sin3θ+2sinθ+sin2θ=0
Solve for sin 2θ using the identity sin 2θ = 2 sin θ cos θ:
−4sin3θ+2sinθ+2sinθcosθ=0
Factor to find zeros and solve for values of θ.
The angles satisfying this equation within the range can be found through numerical methods or further analysis.
Step 4
Use the binomial theorem to expand (1 + x)ᵖ + (1 + x)ᵏ, and hence write down the term of (1 + x)ᵖ + q * x² which is independent of x.
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Answer
Expanding using the binomial theorem:
(1+x)p+q=∑k=0p+q(kp+q)xk
To find the term independent of x, set k = 0. The required term in the combined expansion will be the constant term found in the overall expansion.
Step 5
Given that (1 + x)ᵖ + q * (1 + x)ᵖ = (1 + x)ᵖ * (1 + 1/x), apply the binomial theorem and the result of part (i) to find a simpler expression.
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Answer
From the earlier part, we know how to expand (1 + x)ᵖ:
Rewrite the new expression:
(1+x)p(1+xq)=(1+x)p+q∗x2
Apply the binomial expansion to the right side:
=(1+x)p+q∗x2
Combine terms from both expansions and isolate those involving x and independent terms to simplify further.