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RonnyDeKoning
By the doublingsformulas there are 3 kinds for Cos 2 Aplha, which one do i need to use?
do you know the formula for cos 2A?
|dw:1353240750557:dw| Which i have to use when?
ok good, which one do you need to use? it depends on what you are trying to solve
If i got fore eg: the sinus given I need to use the 3rth, there 3 different formulas?
for example you are trying to prove an identity that has a sine functions, then you can try to use the 3rd formula
but if it involves cosines functions then use the 2nd formula
ok...thnx ...:D good luck now ':D