# How to remember all the trigonometric functions of sum and difference of two angles without rote memorizing it!

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by lfstone3

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by lfstone3

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As you solve, see the patterns and try to visualise them.

For example:

sin(A+B) = sinAcosB+cosBsinA

cos(A+B) = cosAcosB+sinAsinB

Here, you see that for both, formula contains summation of two terms and each term is multiplication of two terms. It is common in both. What is different?

for sin - sin and cos terms are mixed(sinAcosB and cosAsinB)

for cos - sin and cos terms are separate (cosAcosB and sinAsinB)

You form your own patterns which you can remember.