SPM 2018 Add Maths Paper 1, Question 11Trigonometric Functions

Solved on video in English and Bahasa Melayu · 3 marks · Form 5, Trigonometric Functions · 5:13 video

The question

(a) Given cos θ = h, state cos(180° − θ) in terms of h. (b) Diagram 4 shows part of the graph y = (3/2) sin 6α. State the value of p and of q.

[3 marks]

Step 1

Recall the supplementary-angle identity cos(180° − θ) = cos180°cosθ + sin180°sinθ = (−1)(cosθ) + (0)(sinθ) = −cosθ.

Why this step

The formula splits 180° − θ into cos 180° and sin 180°, which we know exactly. That's where the negative sign comes from, so don't answer h.

6 more steps, each with the reason for it, in the full solution

Final answer

(a) −h; (b) p = −3/2, q = π/6

Where students lose marks

Watch out: cos(180° − θ) is −h, not h; p is the signed minimum −3/2; q is half the period, π/6, not π/3.

Watch every step of this question solved on video (5:13), with the reason behind each step and a box that checks your own answer.

No card. Every past-year question on video, in English and BM.