Trigonometry Song

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Found this when I was in 10th grade been using it since:

For sin(a+b)= sin(a)cos(b)+cos(a)sin(b)
Say out loud: “sine cosine cosine sine”

For cos(a+b)= cos(a)cos(b)-sin(a)sin(b)
Say out loud: “cosine cosine SIGN sine sine”
Notice the word “SIGN”. The word SIGN is there to remind you that the SIGN of the rightmost term has the opposite SIGN of the input to the cosine on the left hand side of the equation (if its a+b, then subtract. if its a-b, then add).

Just say it out loud like 3 times. It has a really nice rythm:

“Sine Cosine Cosine Sine”
“Cosine Cosine SIGN Sine Sine”
“Sine Cosine Cosine Sine”
“Cosine Cosine SIGN Sine Sine”
“Sine Cosine Cosine Sine”
“Cosine Cosine SIGN Sine Sine”

from khan academy