Secondary 3 Elementary Math (15 year olds)

Secondary 3 Elementary Math (15 year olds)

Topic 6.3 - Sine Rule

Topic 6.3. Further Trigonometry – Sine Rule

\(\frac{a}{\sin{A}} = \frac{b}{\sin{B}} = \frac{c}{\sin{C}} \)


\(\frac{\sin{A}}{a} = \frac{\sin{B}}{b} = \frac{\sin{C}}{c} \)

Where A, B and C are the three interior angles of \(\Delta \) ABC opposite the sides whose lengths are a, b, and c respectively. This is the Sine Rule.

The video above slows you how to use the Sine Rule and also a simple proof of the rule.

ManyTutors Academy provides free math lessons to the world based on the official Singapore Math syllabus. See how Singapore students learn math!


Feel free to leave comments and I will help when I can.


This Secondary 3 Elementary Maths video series is EXACTLY what Singapore students go through when they are 15 years old. We will provide free math videos to the world based on the entire official Singapore Math syllabus.

If you are a Singapore student who did not manage to follow a specific topic, you can catch up using these video lessons too.

Secondary 3 E-Maths (For 15 year olds)


This course is currently ongoing, I will try to upload a new video each week.


(Optional): We are using the Shinglee New Syllabus Mathematics 3 (7th edition) for Secondary 3 students and you may want to buy this textbook if you are outside Singapore. Otherwise, you will already have the textbook if you are schooling in Singapore.

New Syllabus Mathematics is a series of textbooks specially designed to provide valuable learning experiences to engage the hearts and minds of students sitting for the GCE O level examination in Mathematics. Included in the textbooks are Investigation, Class Discussion, Thinking Time, Journal Writing, Performance Task and Problems in Real-world Contexts to support the teaching and learning of Mathematics.


ManyTutors Academy provides free math education to the world based on the official Singapore Math syllabus.

Inspired by the Khan Academy, we will attempt to make the world renowned Singapore’s education accessible to the rest of the world. Students who follow our entire series should be able to take the Cambridge O-Levels examinations or the K1-K12 exams in the own country.


Course Features

  • Lectures 30
  • Quizzes 0
  • Duration 3 hours
  • Skill level Secondary 3
  • Language English
  • Students 273
  • Assessments Self
Weichang Lai

National University of Singapore B.Sc (Hons) Physics

Hi, my name is Weichang Lai. I am an Adjunct Lecturer teaching Engineering Mathematics / Physics at Nanyang Polytechnic (NYP), School of Engineering. This video series is inspired partly because many of my diploma students are weak in Math and they have no place to turn to when they want to strengthen their foundation. If you are a Singapore student who did not manage to follow a specific topic in class, or a student outside Singapore who wants to be exposed to Singapore Math, feel free to follow my courses too. I will put the entire O-Levels syllabus online so that anyone can learn from these videos. I am also the co-founder of ManyTutors.


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