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5. (a) Find the exact value of the volume of the solid of revolution formed when the region bounded by the curve $y=\sin 2x$, the $x$-axis and the line $x=\frac{\pi}{8}$ is rotated about the $x$-axis - HSC - SSCE Mathematics Extension 1 - Question 5 - 2005 - Paper 1

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5.-(a)-Find-the-exact-value-of-the-volume-of-the-solid-of-revolution-formed-when-the-region-bounded-by-the-curve-$y=\sin-2x$,-the-$x$-axis-and-the-line-$x=\frac{\pi}{8}$-is-rotated-about-the-$x$-axis-HSC-SSCE Mathematics Extension 1-Question 5-2005-Paper 1.png

5. (a) Find the exact value of the volume of the solid of revolution formed when the region bounded by the curve $y=\sin 2x$, the $x$-axis and the line $x=\frac{\pi}... show full transcript

Worked Solution & Example Answer:5. (a) Find the exact value of the volume of the solid of revolution formed when the region bounded by the curve $y=\sin 2x$, the $x$-axis and the line $x=\frac{\pi}{8}$ is rotated about the $x$-axis - HSC - SSCE Mathematics Extension 1 - Question 5 - 2005 - Paper 1

Step 1

When does the particle first reach its maximum speed although some were unsure with their answer given that $v(0) = 0$.

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Answer

To find the time when maximum speed occurs, we first need to derive the velocity function ( v(t) ). Given: x=5+3sin3tcos3tx = 5 + \sqrt{3}\sin 3t - \cos 3t, we find:

v(t)=dxdt=33cos3t+3sin3t.v(t) = \frac{dx}{dt} = 3\sqrt{3}\cos 3t + 3\sin 3t.

Setting ( v(t) = 0 ) to find points of zero velocity does not indicate maximum speed directly. Instead, the maximum speed occurs when the derivative of the sine and cosine terms maximize, with:

3[R]=3(3)2+(1)2=34=6.3[R] = 3 \sqrt{(\sqrt{3})^2 + (-1)^2} = 3\sqrt{4} = 6.

However, a common error is to mistakenly assume maximum speed occurs at (v(0) = 0). The first instance occurs when:

3t=π2extforthemaximumofcos(3t)3t = \frac{\pi}{2} ext{ for the maximum of } cos(3t) which indicates:

t=π6.t = \frac{\pi}{6}.

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