Pythagoras’ theorem, sine, cosine and tangent in right-angled triangles, finding sides and angles, and angles of elevation and depression.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
How tall is that building without climbing it? Measure the distance and the angle, and one button on your calculator does the rest.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
See the squares on the sides, then the trigonometric ratios.
Copy these into your notebook in your own words — that is how they stick.
c² = a² + b² (c = hypotenuse). Hypotenuse: add squares. Shorter side: subtract.
3-4-5; 5-12-13; 8-15-17; 7-24-25 and multiples.
Hypotenuse opposite the right angle; opposite and adjacent relative to the angle.
sin θ = O/H; cos θ = A/H; tan θ = O/A (SOH CAH TOA).
Choose the ratio with the known and unknown sides; rearrange; use degree mode.
θ = sin⁻¹, cos⁻¹ or tan⁻¹ of the ratio.
Measured from the horizontal; equal alternate angles. Add the height of the observer’s eyes.
3 significant figures for lengths, 1 decimal place for angles, unless told otherwise.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Mathematics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (16 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [8 marks]
In triangle ABC, angle B = 90°, AB = 9 cm and BC = 12 cm.
(a) Calculate the length of AC. [2]
(b) Calculate the size of angle BAC, correct to 1 decimal place. [3]
(c) Hence state the size of angle ACB and calculate the area of the triangle. [3]
Question 2 [8 marks]
A student whose eyes are 1.5 m above the ground stands 20 m from the foot of a tree. The angle of elevation of the top of the tree is 35°.
(a) Draw a sketch showing the information (right-angled triangle with 20 m, 35° and the unknown height marked). [2]
(b) Calculate the height of the tree to 1 decimal place. [3]
(c) From the top of a 50 m cliff the angle of depression of a boat is 25°. Calculate the horizontal distance of the boat from the foot of the cliff, to 1 decimal place. [3]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.