Trigonometric Equations (OCR AS Maths A: Pure): Exam Questions

Solve the equation  2 sin $2\theta =1$ for  $0°\le \theta \le 360°$.

Show that the equation  $2$ sin² $x$$+3$ cos $x$$=0$  can be written in the form  $a$ cos² $x$$+b$ cos $x$$+c=0$ , where $a$, $b$ and $c$ are integers to be found.

Hence, or otherwise, solve the equation  $2$sin² $x+3$cos $x=0$  for  $-180°\le x\le 180°$.

Given that $\sin \theta =\frac{3}{5}$  find the possible values of $\cos \theta$ and $\tan \theta$.

Solve the equation  $2$ sin $x$$=\frac{1}{\sin x}$  for  $0°\le x\le 360°$.

Solve the equation $2$ sin $x$ cos $x$$=$cos $x$ for  $-180°\le x\le 180°$.

A right-angled triangle has hypotenuse 8 cm.  One of its other sides is 5 cm.

Find exact values for $\sin \theta$, $\cos \theta$ and $\tan \theta$, where $\theta$ is the smallest angle in the triangle.

Show that $\left(x+1\right)\left(x-2\right)\left(x-3\right)\equiv x^3-4x^2+x+6$.

Hence, or otherwise, solve the equation tan³ $x$$-4$ tan² $x$$+$tan $x$$+6=0$  for  $0°\le x\le 360°$, giving your answers to 1 decimal place where appropriate.

A seagull sits on the surface of the sea and moves up and down as waves pass.

Its height, $h$ metres, above its position in calm water is modelled by the function $h=\frac{1}{2}$sin$\left(180t\right)°$  where $t$ is the time in seconds after timing commences.

Sketch a graph of $h$ against $t$ for $0\le t\le 10$ showing the coordinates of the points of intersection with the $t$ axis.

How many times in the first minute after timing commences is the seagull 0.25 metres above its calm water position?

Find the time at which the seagull is first 0.25m above its calm water position and moving downwards. Give your answer to 3 significant figures.

Solve the equation $2$ sin $\theta$$=3$ cos $\theta$  for $0°\le \theta \le 360°$, giving your answers to 1 decimal place.

Solve the equation  $2$ sin² $\theta$$=$cos $\theta$$+1$ for  $-180°\le \theta \le 180°$

Given that the angle $\theta$ is obtuse and that  sin$\theta =\frac{3}{4}$ , find the exact value of cos $\theta$.

Solve the equation $\tan 2x=\frac{3}{\tan 2x}$  for $-180°\le x\le 180°$ .

Solve the equation  $2$tan $x-$sin $x=0$  for  $-180°\le x\le 180°$.

An isosceles triangle has sides 8 cm, 8 cm and 4 cm and equal base angles $\theta$.

Find exact values for sin $\theta$,cos $\theta$ and tan $\theta$.

Show that  $x=\frac{1}{2}$  satisfies the equation  $8x^3-4x^2-6x+3=0$.

Hence solve the equation $8$ cos³ $x-4$ cos² $x-6$ cos $x+3=0$  for $0°\le x\le 360°$.

A seagull sits on the surface of the sea and moves up and down as waves pass.

Its height, $h$ metres, above its position in calm water is modelled by the function  $h=\frac{2}{5}$sin$\left(180t\right)°$  where $t$ is the time in seconds after timing commenced.

Find the first time the seagull is 0.3 metres above its calm water position.
Give your answer to 2 decimal places.

How many times in the first minute after timing commences is the seagull 0.3 metres above its calm water position?

Solve the equation  $3$ sin $3\theta$$=4$ cos $3\theta$  for $0°\le \theta \le 180°$ , giving your answers to 1 decimal place.

Solve the equation $6$cos² $2\theta$$=$sin $2\theta +5$  for $-180°\le \theta \le 180°$, giving your answers to 1 decimal place where appropriate.

Given that the angle $\theta$ is reflex and that cos $\theta =\frac{1}{3}$  , find the exact value of tan $\theta$.

Solve the equation   $2$sin² $3x=1$  for  $-90°\le x\le 90°$.

Solve the equation  $3$ sin$\left(2x+30°\right)$$=$tan$\left(2x+30°\right)$   for  $-180°\le x\le 180°$, giving your answers to 1 decimal place where appropriate.

For the triangle in the diagram find exact values for sin $x$,cos $x$ and tan $x$.

Find all the values of $x$ in the range $0°\le x\le 180°$  which satisfy the equation  $6$tan³ $2x-7$tan² $2x-$tan $2x+2=0$, giving your answers to 1 decimal place.

A seagull sits on the surface of the sea and moves up and down as waves pass.

Its height, $h$ metres, above its position in calm water is modelled by the function  $h=\frac{3}{5}\sin \left(90t\right)°$ where $t$ is the time in seconds after timing commences.

Find the amount of time the seagull is more than 0.5 metres above its calm water position in the first 20 seconds after timing commences.

Give your answer correct to 3 significant figures.