SPM 2021 Add Maths Paper 1, Question 1Circular Measure

Solved on video in English and Bahasa Melayu · Form 5, Circular Measure · 3:15 video

The question

Diagram 1 shows an arc AB which subtends an angle of π/3 rad at the centre of the circle O. The radius of the circle is 2 cm. Find the area, in cm², of the major sector OAB in terms of π.

SPM 2021 Add Maths Paper 1, Question 1: the question as drawn in Eduly's video3:15

Step 1

The major sector angle is the full angle of the circle minus the minor sector angle: 2π − π/3.

Why this step

The major sector is the rest of the circle. A full turn is 2π, so we remove the minor sector's π/3 from it.

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

Final answer

10π/3 cm²

Where students lose marks

Watch out: give the area in terms of π (10π/3), not a decimal, and write the unit as cm², not m².

Watch every step of this question solved on video (3:15), with the reason behind each step and a box that checks your own answer.

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Circular Measure: lessons and every past-year question

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