Prove derivative formula

5 Prove by mathematical induction that, for every positive integer \(n\), $$\frac { d ^ { 2 n - 1 } } { d x ^ { 2 n - 1 } } ( x \sin x ) = ( - 1 ) ^ { n - 1 } ( x \cos x + ( 2 n - 1 ) \sin x )$$

2 It is given that \(\mathrm { y } = \mathrm { xe } ^ { \mathrm { ax } }\), where \(a\) is a constant.
Prove by mathematical induction that, for all positive integers \(n\), $$\frac { d ^ { n } y } { d x ^ { n } } = \left( a ^ { n } x + n a ^ { n - 1 } \right) e ^ { a x }$$

4 The function f is such that \(\mathrm { f } ^ { \prime \prime } ( x ) = \mathrm { f } ( x )\).
Prove by mathematical induction that, for every positive integer \(n\), $$\frac { d ^ { 2 n - 1 } } { d x ^ { 2 n - 1 } } ( x f ( x ) ) = x f ^ { \prime } ( x ) + ( 2 n - 1 ) f ( x )$$

2 Prove by mathematical induction that, for all positive integers \(n\), $$\frac { d ^ { n } } { d x ^ { n } } \left( x ^ { 2 } e ^ { x } \right) = \left( x ^ { 2 } + 2 n x + n ( n - 1 ) \right) e ^ { x }$$

2 Prove by mathematical induction that, for all positive integers \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \tan ^ { - 1 } x \right) = P _ { n } ( x ) \left( 1 + x ^ { 2 } \right) ^ { - n } ,$$ where \(P _ { n } ( x )\) is a polynomial of degree \(n - 1\). \includegraphics[max width=\textwidth, alt={}, center]{99ac7fe2-184b-4a72-89f6-03fe4b2af138-05_2726_35_97_20}

2 Prove by mathematical induction that, for all positive integers \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \tan ^ { - 1 } x \right) = P _ { n } ( x ) \left( 1 + x ^ { 2 } \right) ^ { - n } ,$$ where \(P _ { n } ( x )\) is a polynomial of degree \(n - 1\). \includegraphics[max width=\textwidth, alt={}, center]{beb69d0f-3f83-49bf-b9a2-329ddc7243fa-04_2718_42_107_2007} \includegraphics[max width=\textwidth, alt={}, center]{beb69d0f-3f83-49bf-b9a2-329ddc7243fa-05_2726_35_97_20}

3 Prove by mathematical induction that, for every positive integer \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \mathrm { e } ^ { x } \sin x \right) = ( \sqrt { } 2 ) ^ { n } \mathrm { e } ^ { x } \sin \left( x + \frac { 1 } { 4 } n \pi \right)$$

2 Prove by mathematical induction that, for all positive integers \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \frac { 1 } { 2 x + 3 } \right) = ( - 1 ) ^ { n } \frac { n ! 2 ^ { n } } { ( 2 x + 3 ) ^ { n + 1 } }$$

3

1. Show that \(\frac { \mathrm { d } ^ { n + 1 } } { \mathrm {~d} x ^ { n + 1 } } \left( x ^ { n + 1 } \ln x \right) = \frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( x ^ { n } + ( n + 1 ) x ^ { n } \ln x \right)\).
2. Prove by mathematical induction that, for all positive integers \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( x ^ { n } \ln x \right) = n ! \left( \ln x + 1 + \frac { 1 } { 2 } + \ldots + \frac { 1 } { n } \right)$$

6 It is given that \(y = \mathrm { e } ^ { x } u\), where \(u\) is a function of \(x\). The \(r\) th derivatives \(\frac { \mathrm { d } ^ { r } y } { \mathrm {~d} x ^ { r } }\) and \(\frac { \mathrm { d } ^ { r } u } { \mathrm {~d} x ^ { r } }\) are denoted by \(y ^ { ( r ) }\) and \(u ^ { ( r ) }\) respectively. Prove by mathematical induction that, for all positive integers \(n\), $$y ^ { ( n ) } = \mathrm { e } ^ { x } \left( \binom { n } { 0 } u + \binom { n } { 1 } u ^ { ( 1 ) } + \binom { n } { 2 } u ^ { ( 2 ) } + \ldots + \binom { n } { r } u ^ { ( r ) } + \ldots + \binom { n } { n } u ^ { ( n ) } \right)$$ [You may use without proof the result \(\binom { k } { r } + \binom { k } { r - 1 } = \binom { k + 1 } { r }\).]

8
- 2 \end{array} \right) .$$ 6 It is given that \(y = \mathrm { e } ^ { x } u\), where \(u\) is a function of \(x\). The \(r\) th derivatives \(\frac { \mathrm { d } ^ { r } y } { \mathrm {~d} x ^ { r } }\) and \(\frac { \mathrm { d } ^ { r } u } { \mathrm {~d} x ^ { r } }\) are denoted by \(y ^ { ( r ) }\) and \(u ^ { ( r ) }\) respectively. Prove by mathematical induction that, for all positive integers \(n\), $$y ^ { ( n ) } = \mathrm { e } ^ { x } \left( \binom { n } { 0 } u + \binom { n } { 1 } u ^ { ( 1 ) } + \binom { n } { 2 } u ^ { ( 2 ) } + \ldots + \binom { n } { r } u ^ { ( r ) } + \ldots + \binom { n } { n } u ^ { ( n ) } \right)$$ [You may use without proof the result \(\binom { k } { r } + \binom { k } { r - 1 } = \binom { k + 1 } { r }\).]\\ 7 Let $$S _ { N } = \sum _ { r = 1 } ^ { N } ( 3 r + 1 ) ( 3 r + 4 ) \quad \text { and } \quad T _ { N } = \sum _ { r = 1 } ^ { N } \frac { 1 } { ( 3 r + 1 ) ( 3 r + 4 ) } .$$

1. Use standard results from the List of Formulae (MF10) to show that $$S _ { N } = N \left( 3 N ^ { 2 } + 12 N + 13 \right)$$
2. Use the method of differences to show that $$T _ { N } = \frac { 1 } { 12 } - \frac { 1 } { 3 ( 3 N + 4 ) } .$$
3. Deduce that \(\frac { S _ { N } } { T _ { N } }\) is an integer.
4. Find \(\lim _ { N \rightarrow \infty } \frac { S _ { N } } { N ^ { 3 } T _ { N } }\).\\ 8
5. By considering the binomial expansion of \(\left( z + \frac { 1 } { z } \right) ^ { 6 }\), where \(z = \cos \theta + i \sin \theta\), express \(\cos ^ { 6 } \theta\) in the form $$\frac { 1 } { 32 } ( p + q \cos 2 \theta + r \cos 4 \theta + s \cos 6 \theta ) ,$$ where \(p , q , r\) and \(s\) are integers to be determined.
6. Hence find the exact value of $$\int _ { - \frac { 1 } { 2 } \pi } ^ { \frac { 1 } { 2 } \pi } \cos ^ { 6 } \left( \frac { 1 } { 2 } x \right) \mathrm { d } x$$

2 It is given that \(y = \ln ( a x + 1 )\), where \(a\) is a positive constant. Prove by mathematical induction that, for every positive integer \(n\), $$\frac { \mathrm { d } ^ { n } y } { \mathrm {~d} x ^ { n } } = ( - 1 ) ^ { n - 1 } \frac { ( n - 1 ) ! a ^ { n } } { ( a x + 1 ) ^ { n } }$$

3 Given that \(a\) is a constant, prove by mathematical induction that, for every positive integer \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( x \mathrm { e } ^ { a x } \right) = n a ^ { n - 1 } \mathrm { e } ^ { a x } + a ^ { n } x \mathrm { e } ^ { a x }$$

3 Prove by induction that, for all \(n \geqslant 1\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \mathrm { e } ^ { x ^ { 2 } } \right) = \mathrm { P } _ { n } ( x ) \mathrm { e } ^ { x ^ { 2 } } ,$$ where \(\mathrm { P } _ { n } ( x )\) is a polynomial in \(x\) of degree \(n\) with the coefficient of \(x ^ { n }\) equal to \(2 ^ { n }\).

3 Prove by mathematical induction that, for all positive integers \(n\), $$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \mathrm { e } ^ { x } \sin x \right) = 2 ^ { \frac { 1 } { 2 } n } \mathrm { e } ^ { x } \sin \left( x + \frac { 1 } { 4 } n \pi \right)$$

5 It is given that \(y = ( 1 + x ) ^ { 2 } \ln ( 1 + x )\). Find \(\frac { \mathrm { d } ^ { 3 } y } { \mathrm {~d} x ^ { 3 } }\). Prove by mathematical induction that, for every integer \(n \geqslant 3\), $$\frac { \mathrm { d } ^ { n } y } { \mathrm {~d} x ^ { n } } = ( - 1 ) ^ { n - 1 } \frac { 2 ( n - 3 ) ! } { ( 1 + x ) ^ { n - 2 } }$$

6 Let \(\mathrm { y } = \mathrm { x } \cosh \mathrm { x }\).
Prove by induction that, for all integers \(n \geqslant 1 , \frac { d ^ { 2 n - 1 } y } { d x ^ { 2 n - 1 } } = x \sinh x + ( 2 n - 1 ) \cosh x\).