The teacher will be very surprised to see your correct solution 😉
sum
-acos(2/3) + 2*pi + acos(2/3)
=
2*pi
product
(-acos(2/3) + 2*pi)*acos(2/3)
=
(-acos(2/3) + 2*pi)*acos(2/3)
(-acos(2/3) + 2*pi)*acos(2/3)
x1 = -acos(2/3) + 2*pi
x2 = acos(2/3)
x2 = acos(2/3)
x1 = -19.6906245921067
x2 = 43.1412284796892
x3 = -74.5571550155871
x4 = -36.8580431725096
x5 = 5.44211663661166
x6 = -5.44211663661166
x7 = 51.1065511280046
x8 = 88.8056629710821
x9 = 25.9738098992863
x10 = -63.6729217423638
x11 = -76.239292356723
x12 = 32.2569952064659
x13 = -101.372033585441
x14 = -49.4244137868688
x15 = 24.2916725581504
x16 = -13.4074392849271
x17 = -57.3897364351842
x18 = 63.6729217423638
x19 = 87.1235256299463
x20 = -44.823365820825
x21 = 68.2739697084075
x22 = -25.9738098992863
x23 = 44.823365820825
x24 = -68.2739697084075
x25 = 13.4074392849271
x26 = 61.9907844012279
x27 = -82.5224776639025
x28 = -88.8056629710821
x29 = 7.12425397774752
x30 = -87.1235256299463
x31 = -69.9561070495434
x32 = 76.239292356723
x33 = 38.5401805136454
x34 = -80.8403403227667
x35 = -43.1412284796892
x36 = 49.4244137868688
x37 = 18.0084872509708
x38 = 95.0888482782617
x39 = -30.57485786533
x40 = 69.9561070495434
x41 = 30.57485786533
x42 = 74.5571550155871
x43 = -55.7075990940483
x44 = 0.84106867056793
x45 = -61.9907844012279
x46 = -0.84106867056793
x47 = -18.0084872509708
x48 = 55.7075990940483
x49 = 82.5224776639025
x50 = 57.3897364351842
x51 = 80.8403403227667
x52 = 19.6906245921067
x53 = -93.4067109371259
x54 = -95.0888482782617
x55 = -51.1065511280046
x56 = -11.7253019437912
x57 = -99.6898962443055
x58 = -32.2569952064659
x59 = -7.12425397774752
x60 = 11.7253019437912
x61 = -38.5401805136454
x62 = 36.8580431725096
x63 = 93.4067109371259
x64 = 99.6898962443055
x65 = -24.2916725581504
x65 = -24.2916725581504