Break, Trigonometric Function Formula!

Today, I’ll post something about trigonometric functions.

I found a useful posting about this but it’s in Korean so my work will merely translating them.

You can check it here if you can read Korean.

First, we will look at the form of ” asinx + bcosx”.

Note that the angles of sin and cos are same.

Think about a circle with 1 radius and its cross point between the vector (a,b)

Then cosΘ is the x-coordinate and sinΘ is the y-coordinate.

Hence, we can prove the formula like the above.

Addition, subtraction etc of trigonometric functions.

The proof is like below.

The reason of A is below

You can get other formula by using the first one.

e.g., but -B instead of B in the first formula.

 So you need to remember only first one.

There are three 2 and 2 things to alternate (sin -> cos, + -> -)

I’ll upload about this if I need it.


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