Quadratic in sin²/cos²/tan²

Solve equations that are quadratic in sin² θ, cos² θ, or tan² θ (or equivalent substitutions like x = sin² θ).

10 questions · Moderate -0.5

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CAIE P1 2020 November Q3
5 marks Standard +0.3
3 Solve the equation \(3 \tan ^ { 2 } \theta + 1 = \frac { 2 } { \tan ^ { 2 } \theta }\) for \(0 ^ { \circ } < \theta < 180 ^ { \circ }\).
CAIE P1 2024 November Q4
4 marks Moderate -0.3
4 Solve the equation \(4 \sin ^ { 4 } \theta + 12 \sin ^ { 2 } \theta - 7 = 0\) for \(0 ^ { \circ } \leqslant \theta \leqslant 360 ^ { \circ }\).
CAIE P1 2011 June Q5
6 marks Moderate -0.3
5
  1. Show that the equation \(2 \tan ^ { 2 } \theta \sin ^ { 2 } \theta = 1\) can be written in the form $$2 \sin ^ { 4 } \theta + \sin ^ { 2 } \theta - 1 = 0 .$$
  2. Hence solve the equation \(2 \tan ^ { 2 } \theta \sin ^ { 2 } \theta = 1\) for \(0 ^ { \circ } \leqslant \theta \leqslant 360 ^ { \circ }\).
CAIE P1 2003 November Q2
5 marks Moderate -0.3
2
  1. Show that the equation \(4 \sin ^ { 4 } \theta + 5 = 7 \cos ^ { 2 } \theta\) may be written in the form \(4 x ^ { 2 } + 7 x - 2 = 0\), where \(x = \sin ^ { 2 } \theta\).
  2. Hence solve the equation \(4 \sin ^ { 4 } \theta + 5 = 7 \cos ^ { 2 } \theta\), for \(0 ^ { \circ } \leqslant \theta \leqslant 360 ^ { \circ }\).
OCR MEI C2 Q7
5 marks Moderate -0.3
7 Showing your method clearly, solve the equation \(4 \sin ^ { 2 } \theta = 3 + \cos ^ { 2 } \theta\), for values of \(\theta\) between \(0 ^ { \circ }\) and \(360 ^ { \circ }\).
Edexcel C2 Q3
6 marks Moderate -0.8
3. Giving your answers in terms of \(\pi\), solve the equation $$3 \tan ^ { 2 } \theta - 1 = 0 ,$$ for \(\theta\) in the interval \(- \pi \leq \theta \leq \pi\).
OCR C2 Q1
5 marks Moderate -0.8
  1. Giving your answers in terms of \(\pi\), solve the equation
$$3 \tan ^ { 2 } \theta - 1 = 0 ,$$ for \(\theta\) in the interval \(- \pi \leq \theta \leq \pi\).
OCR H240/02 2020 November Q4
5 marks Standard +0.3
4 In this question you must show detailed reasoning.
Solve the equation \(3 \sin ^ { 4 } \phi + \sin ^ { 2 } \phi = 4\), for \(0 \leqslant \phi < 2 \pi\), where \(\phi\) is measured in radians.
AQA AS Paper 2 2018 June Q4
4 marks Moderate -0.8
4 Solve the equation \(\tan ^ { 2 } 2 \theta - 3 = 0\) giving all the solutions for \(0 ^ { \circ } \leq \theta \leq 360 ^ { \circ }\) [0pt] [4 marks] \(5 \quad \mathrm { f } ^ { \prime } ( x ) = \left( 2 x - \frac { 3 } { x } \right) ^ { 2 }\) and \(\mathrm { f } ( 3 ) = 2\) Find \(\mathrm { f } ( x )\).
[0pt] [4 marks]
AQA Paper 1 2024 June Q5
3 marks Easy -1.8
5 Solve the equation $$\sin ^ { 2 } x = 1$$ for \(0 ^ { \circ } < x < 360 ^ { \circ }\) [0pt] [3 marks]