The teacher will be very surprised to see your correct solution 😉
/x\ /pi\ sin|-| = cos|--| \2/ \8 /
3*pi x1 = ---- 4
5*pi x2 = ---- 4
sum
3*pi 5*pi 0 + ---- + ---- 4 4
=
2*pi
product
3*pi 5*pi 1*----*---- 4 4
=
2 15*pi ------ 16
15*pi^2/16
x1 = -46.3384916404494
x2 = 52.621676947629
x3 = -96.6039740978861
x4 = 16.4933614313464
x5 = -47.9092879672443
x6 = 90.3207887907066
x7 = 102.887159405066
x8 = -110.74114103904
x9 = -12124.1914483664
x10 = 781.471172580461
x11 = -84.037603483527
x12 = -73.0420291959627
x13 = -58.9048622548086
x14 = 3.92699081698724
x15 = 2.35619449019234
x16 = -85.6083998103219
x17 = 253.683606777376
x18 = 77.7544181763474
x19 = -98.174770424681
x20 = -8.63937979737193
x21 = 40.0553063332699
x22 = -33.7721210260903
x23 = 41.6261026600648
x24 = 230.121661875452
x25 = -35.3429173528852
x26 = 27.4889357189107
x27 = -21.2057504117311
x28 = 91.8915851175014
x29 = 66.7588438887831
x30 = -22.776546738526
x31 = -10.2101761241668
x32 = 519.148186005713
x33 = 505.011019064559
x34 = 79.3252145031423
x35 = -60.4756585816035
x36 = 65.1880475619882
x37 = 29.0597320457056
x38 = 54.1924732744239
x39 = -71.4712328691678
x40 = 14.9225651045515
x40 = 14.9225651045515