Derivation of high school math formulas, will come, no nonsense 50

a+b+c=, thus a+b= -c, a2+b2= 2-c2, by the induction formula has: sin = sin( -cos = -cos( -sin( )=cos( 2-).

Just substitute it.

It's a lot.

This is the only way to find :

Give me some formulas that you don't remember very well! It's hard for us to do that like you.

Push it yourself, push it yourself and be impressed, it's not easy to forget! ~

It's trigonometric functions.

Know sina

The rest of the analogy is here.

sina=2sin(a/2)cos(a/2)=[2sin(a/2)cos(a/2)]/[sin^2(a/2)+cos^2(a/2)]

The numerator denominator is divided by cos 2 (a2) at the same time

2sin(a/2)cos(a/2)/cos^2(a/2)]/[(sin^2(a/2)+cos^2(a/2))/cos^2(a/2)]

Simplify: =[2sin(a 2) cos(a 2)] [sin 2(a 2) cos 2(a 2)+1].

i.e.: =(2tan(a 2)) (tan (a 2)+1).

Yes, basically all of them.

There is a textbook, look at it yourself, it is the most complete written on it.

It's a trigonometric function, you know sina The other analogy is sina = 2 sin(a 2)cos(a 2).

2sin(a/2)cos(a/2)]/[sin^2(a/2)+cos^2(a/2)]

The numerator denominator is divided by cos 2 (a2) at the same time

2sin(a/2)cos(a/2)/cos^2(a/2)]/[(sin^2(a/2)+cos^2(a/2))/cos^2(a/2)]

Simplify: =[2sin(a 2) cos(a 2)] [sin 2(a 2) cos 2(a 2)+1].

i.e.: =(2tan(a 2)) (tan (a 2)+1).

Medium, useless, I don't think it's necessary to explore the process really! Just remember the formula.