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1919 Paper 4 Q401
D: 1500.0 B: 1500.0

Find the conditions that \(ax^2+2hxy+by^2+2gx+2fy+c\) should

  1. [(i)] split up into two linear factors,
  2. [(ii)] be a complete square.
Eliminate \(x\) and \(y\) from \[ x^2+xy=a^2, \quad y^2+xy=b^2, \quad x^2+y^2=c^2. \]

1919 Paper 4 Q402
D: 1500.0 B: 1500.0

Shew how to express \(ax^2+2bx+c\) and \(a'x^2+2b'x+c'\) simultaneously in the forms \(p(x-\alpha)^2+q(x-\beta)^2\) and \(p'(x-\alpha)^2+q'(x-\beta)^2\). Apply your method to \[ 7x^2-22x+28 \quad \text{and} \quad 27x^2-62x+68. \]

1919 Paper 4 Q403
D: 1500.0 B: 1500.0

Prove that \[ \log_e(1+x)=x-\frac{x^2}{2}+\frac{x^3}{3}-\dots. \] Sum the series \[ \sum_{n=0}^{n=\infty} \frac{(3n+2)}{n^2+3n+2}x^n. \]

1919 Paper 4 Q404
D: 1500.0 B: 1500.0

Prove the rule for finding successive convergents of the continued fraction \[ \frac{1}{a_1+} \frac{1}{a_2+} \frac{1}{a_3+} \dots. \] In the recurring continued fraction \[ \frac{1}{1+} \frac{1}{2+} \frac{1}{3+} \frac{1}{1+} \frac{1}{2+} \frac{1}{3+} \dots, \] prove that \(3p_{3n}=2q_{3n}+q_{3n-3}\).

1919 Paper 4 Q405
D: 1500.0 B: 1500.0

Prove Wilson's theorem that \((n-1)!+1\) is divisible by \(n\) when \(n\) is a prime. Prove that \(\frac{72!}{(36!)^2}-1\) is divisible by 73.

1919 Paper 4 Q406
D: 1500.0 B: 1500.0

State Maclaurin's theorem on the expansion of a function \(f(x)\) in ascending powers of \(x\). If \(y=e^{\sin^{-1}x}\) and \(y_n\) denote the \(n\)th differential coefficient of \(y\) with respect to \(x\), prove that, when \(x=0\), \(y_{n+2}=(n^2+1)y_n\), and hence expand \(y\) in ascending powers of \(x\).

1919 Paper 4 Q407
D: 1500.0 B: 1500.0

Explain how the maxima and minima values of a function \(f(x)\) may be obtained. A right circular cone with axis vertical is drawn to circumscribe a sphere of radius \(a\) resting on a horizontal plane, the base of the cone also resting on the plane. Prove that the minimum volume of the cone is twice the volume of the sphere. Shew also that the sum of the areas of the curved surface of the cone and of its plane base is a minimum at the same time.

1919 Paper 4 Q408
D: 1500.0 B: 1500.0

Prove that in polar coordinates \(r\frac{d\theta}{dr}\) is the tangent of the angle between the radius vector and tangent to a curve. In the case of the curve \(r^n=a^n\cos n\theta\), prove that \(a^n\frac{d^2r}{ds^2}+nr^{2n-1}=0\).

1919 Paper 4 Q409
D: 1500.0 B: 1500.0

Evaluate \[ \int_0^\infty x^2\sin x, \quad \int_0^\infty \frac{xdx}{(1+x)(1+x^2)}, \quad \int_a^b \frac{dx}{(a+b-x)^2\sqrt{(x-a)(b-x)}} \quad (b>a). \] Find a formula of reduction connecting \[ \int \cos m\theta \cos^n\theta d\theta \quad \text{with} \quad \int \cos m\theta \cos^{n-2}\theta d\theta. \]

1919 Paper 4 Q410
D: 1500.0 B: 1500.0

Trace the curve \[ x(y^2-\frac{1}{2}a^2) - y(x^2-\frac{1}{2}a^2) = a^3, \] and shew that the radius of curvature where it meets either axis is \(\frac{25}{12}a\sqrt{2}\).