try this site for the basic idea of the curves.
http://curvebank.calstatela.edu/unit/unit.htmif you draw a circle and divide into quarters or four 'quadrants' it looks something like below:
90
S | A
180----------0/360
T | C
270
each quadrant is labelled to represent what is positive in that quadrant:
1) A=All +ve , S= Sin +ve , T=Tan +ve , C=Cos +ve
2) This shows the four quadrants, going anticlockwise from 0 to 90 to 180 270 to 360.
you can test this out to familiarise yourself with it. do sin or cos or tan of any number between 0-90 on your calc and you'll get a positive answer.
do sin of any no from 90-180--> positive
tan of any no form 180-270--> positive
cos of any no form 270-360-->positive
ok. the actual question:
a)
sinx=sin 50
x=50degrees
they want the angle between 90 and 180 that'll give you the same answer. The angle already given to us is in the 1st quadrant, so now we know we will get the same value in the 2nd quadrant with (180-x)
180-50=130degrees
ok i just realised this might be difficult to understand without a diagram if you haven't done this before :/
b)sinx=-sin50
sine is negative in 3rd and 4th quadrants
180+50=230
360-150=310
i'm really sorry if i haven't explained it clearly... hope it helps a little
