Short Inverse Trig question

Just use a calculator to find  (unless you know )

   arcsin (-1/2) = -30 or  210 degrees

arc cos (sqrt2 *3) is invalid

    Arccos(sqrt(3)/2)   is also 30 degrees which is pi/6 radians   ( or - pi/6 radians also)

For the first one...make sure your calculator  [ or our calculator] is set to "degree" mode!!

1.  First of all ...arcsin (-12)  doesn't exist

I think you mean   arcsin (-1/2)  = -30°   = [360 - 30 ]° =  330°  [ positive result ] 

2. arccos(3√2).....I think you mean arccos (√3/ 2)...set your calculator to "radian" mode

arccos(√3/2) ≈ .523 rads

Note.....that on the second one...if we want the exact result...set your calculator back to "degree" mode and evaluate arccos(3√2)  =   30°

To convert this to an exact result....use this

30° x    pi / 180° =   (30/180) pi  = pi/6   (rads)