draw your triangle
the other side is √15
since we are in QII and sin is positive,
x = -√15
y = 1
r = 4
so, cosx = -√15/4
Now use those values to plug into your half-angle formulas.
solve sinx/2,cosx/2 & tanx/2 of the following:-
(a)sinx=1/4 & x lies in second quadrant.
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