C2 Trig question - help!

When doing this question:

I get: (pi/6), (11pi/6), (5pi/6), (7pi/6)

However the mark scheme says the answers are:


Where am I going wrong? or is the mark scheme wrong? As I subbed in the 2 answers I didn't get into the original equation and I got 0 instead of 3/4

Can you show your working out please?

Sure, Ill add it to the op in 1 second.

EDIT: Added

.

it's easier to work in degrees and change at the end ?

for the + root you get 60,120,420,480,...

for the - root you get -60, -120, 300, 240, 660, ....

then just subtract 90 and convert into radions.

it's easier to work in degrees and change at the end ?

for the + root you get 60,120,420,480,...

for the - root you get -60, -120, 300, 240, 660, ....

then just subtract 90 and convert into radions.

I have just quickly given it a go and got the same answers but using a different method, so unless we're both making the same mistake somewhere?...

I suppose the book is probably wrong then, first question I've ever done in this book, so I have great confidence in it thus far.