http://google.com/newsstand/s/CBIw2d2K-Dk

# Tag Archives: Trigonometry

Trigo

# Dr. Adrian Yeo Ning Hong’s Math Books

Dr. Yeo Ning Hong was the former cabinet Minister of Singapore. He wrote a few Math books after retirement to teach his grand-daughters in primary schools – on Trigonometric Identity Proofs !!!

Yes!

He has wonderful tricks to make such difficult Secondary 3 Math easy for kids, and of course, also helps the weak Math teenagers.

Interesting !

Trig Or Treat: An Encyclopedia of Trigonometric Identity Proofs With Intellectually Challenging Games

The other books by him are:

# Beautiful Trigonometry

Beautiful Trigonometry

tan α +tan β +tan γ = tan α.tan β.tan γ

# What is “sin A”

What is “sin A” concretely ?

1. Draw a circle (diameter 1)

2. Connect any 3 points on the circle to form a triangle of angles A, B, C.

3. The length of sides opposite A, B, C are sin A, sin B, sin C, respectively.

Proof:

By Sine Rule:

where sides a,b,c opposite angles A, B, C respectively.

a = sin A

b = sin B

c = sin C