Question

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Answer 1

a=5/4 is in Q3

what is a ? what units ?

Answer 2

well draw a picture in the 3rd quadrant



int he 3rd quadrant cos is also negative, you will need to find the value of x.

since cos is negative in the 3rd quadrant, x will also be negative, which makes sense given its position on the number plane.

so when you get cos(a)

then use

sin(2a) = 2sin(a)cos(a)

just substitute and evaluate

and a = 5/4 doesn't make a lot of sense... unless its tan(a) = 5/4