Hi there im in my final year at high school in Scotland and i am having difficulty with the wave function.

for example in the exercise we are told to write the expression :

a cos x+ b sin x in the form k cos(x-a)

This i had little problem with and was able to work out what quadrant i shoul use etc what i mean is the

all positive. sin positive, tan positive and cosine positivequadrants

but the next exercise was expressing

a cos x + b sin x in other forms such as:

k cos(x+a) k sin(x-a) and k(sin x+a)

with these i am able to work out the k. however when it comes down to the quadrat i do not no whether to take away 180 add 180 or take away 360 if you no what i mean.

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