I used the formula with the central angle in degrees that didn't display when I copied it here.

theta = 2arcsin (c/2R)

c = 1.5 and R = 1, so C/2R = 0.75

arcsin(0.75) = about 48.59 degrees

theta = 2*48.59 = about 97.18 degrees

A = (1^2)/2 (97.18pi/180) - sin(97.18pi/180))

97.18pi/180 = about 1.696

A = 1/2 (1.696 - sin 1.696)

sin 1.696 = about 0.296

A = 1/2 (1.696 - 0.296) = 1/2 (1.666) = 0.833

I prefer degrees to radians, but I feel like I'm converting to radians and then taking sin of 1.696, which is wrong. However, if I change that part to sin of 97.18 degrees, I get an answer that's way too low:

A = (1^2)/2 (97.18pi/180) - sin(97.18pi/180))

97.18pi/180 = about 1.696

A = 1/2 (1.696 - sin 97.18)

sin 97.18 = about 0.992

A = 1/2 (1.696 - 0.992) = 1/2 (0.704) = 0.352