solve sin theta = 1/2,90 degrees less than theta less than 180 degrees

Answer 1

make sure your calculator is set to degrees

2nd
sin
(1/2.9)
= 20.17

You want the angle between 0 and 180, that is in the I or II quadrant.
20.17° is in quadrant I
the angle in quadrant II would be 180 - 20.17 = 159.83°

check:
take the sine of each of those angles and compare it to 1/2.9