Photo AI

Figure 4 shows a sketch of part of the curve C with parametric equations $x = 3 heta ext{sin} heta$, $y = ext{sec} heta$, $0 < heta < \frac{ ext{π}}{2}$ - Edexcel - A-Level Maths Pure - Question 1 - 2005 - Paper 5

Question icon

Question 1

Figure-4-shows-a-sketch-of-part-of-the-curve-C-with-parametric-equations--$x-=-3-heta--ext{sin}-heta$,--$y-=--ext{sec}-heta$,--$0-<--heta-<-\frac{-ext{π}}{2}$-Edexcel-A-Level Maths Pure-Question 1-2005-Paper 5.png

Figure 4 shows a sketch of part of the curve C with parametric equations $x = 3 heta ext{sin} heta$, $y = ext{sec} heta$, $0 < heta < \frac{ ext{π}}{2}$. The ... show full transcript

Worked Solution & Example Answer:Figure 4 shows a sketch of part of the curve C with parametric equations $x = 3 heta ext{sin} heta$, $y = ext{sec} heta$, $0 < heta < \frac{ ext{π}}{2}$ - Edexcel - A-Level Maths Pure - Question 1 - 2005 - Paper 5

Step 1

Find the exact value of k.

96%

114 rated

Answer

To find the value of k, we start by noting that the point P(k, 8) lies on the curve C, where the equations are given as:

x=3θsinθx = 3\theta \text{sin}\theta y=secθy = \text{sec}\theta.

Since y = 8, we set:\n secθ=8\text{sec}\theta = 8 which gives us ( \theta = \text{sec}^{-1}(8) ). Now, we proceed by calculating k:

k=3θsinθ=3sec1(8)sin(sec1(8))k = 3\theta \text{sin}\theta = 3\text{sec}^{-1}(8) \cdot \text{sin} \left(\text{sec}^{-1}(8)\right). To express ( \text{sin} \left(\text{sec}^{-1}(8)\right) ):

From the right triangle definition: ( \text{sin}\theta = \frac{1}{\text{sec}\theta} = \frac{1}{8} ), therefore,

Thus, k=3sec1(8)18=38sec1(8)k = 3 \cdot \text{sec}^{-1}(8) \cdot \frac{1}{8} = \frac{3}{8} \cdot \text{sec}^{-1}(8).

Step 2

Show that the area of R can be expressed in the form $$\lambda\int_{0}^{\alpha} \left( \text{sec}^2\theta + \tan\theta \text{sec}^2\theta \right) d\theta$$.

99%

104 rated

Answer

The area of region R can be obtained using the formula:

Area=ab(f(x))dx\text{Area} = \int_{a}^{b} (f(x)) dx where f(x) is defined by the curve.

Given our parametric equations, we can express the area using:

Area=0ky(x)dx\text{Area} = \int_{0}^{k} y(x) \, dx Substituting for y from the parametric equation, we have:

y=secθy = \text{sec}\theta. We also differentiate x with respect to \theta:

dxdθ=3sinθ+3θcosθ\frac{dx}{d\theta} = 3 \text{sin}\theta + 3\theta\text{cos}\theta. Now, we can express the area in the required form:

0αsec2θdθ+tanθsec2θdθ\int_{0}^{\alpha} \text{sec}^2\theta d\theta + \tan\theta\text{sec}^2\theta d\theta showing that constants \lambda, \alpha, and \beta can be determined later through integration where necessary.

Step 3

Hence use integration to find the exact value of the area of R.

96%

101 rated

Answer

To find the exact area, we evaluate the integral obtained from part (b):

Area=λ0α(sec2θ+tanθsec2θ)dθ\text{Area} = \lambda \int_{0}^{\alpha} ( \text{sec}^2\theta + \tan\theta \text{sec}^2\theta ) d\theta. Using integration techniques, we can work out the integral:

(sec2θ+tanθsec2θ)dθ\int ( \text{sec}^2\theta + \tan\theta \text{sec}^2\theta ) d\theta This integrates to:

Area=[tanθ+12(sec2θ)]0α\text{Area} = \left[ \tan\theta + \frac{1}{2} (\text{sec}^2\theta) \right]_{0}^{\alpha} Evaluating this for the limits and substituting values will yield the exact area of region R.

By substituting the limits after finding \alpha, through attention to the parameters set in the problem, we can calculate the final area.

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;