Question

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Answer 1

@phi

Answer 2

btw, the Greek letter pi is different from apple pie

by compound angle formula I think they mean using
\[ \cos(A \pm B) = \cos A \cos B \mp \sin A \sin B \]

Answer 3

yeah but how do i know which comp angle to use for this question and i think am missong my y value there

Answer 4

good question. I don't think in radians very well, so I change to degrees by multiplying by 180/pi . We get 330 degrees
or -30 degrees

and we don't need to use any formula: cos (-30 deg) = cos (30 deg) = sqr(3)/2

Answer 5

tbh thats exactly what i was thinking i got 330 myself ok so the only thing remianing is related acite angle and a lil bit of trig..i think i got it..

Answer 6

I make a sketch