The teacher will be very surprised to see your correct solution 😉
___ -\/ 2 cos(x) = ------- 2
sum
3*pi 5*pi ---- + ---- 4 4
=
2*pi
product
3*pi 5*pi ---- * ---- 4 4
=
2 15*pi ------ 16
3*pi x_1 = ---- 4
5*pi x_2 = ---- 4
x1 = -335.36501577071
x2 = -85.6083998103219
x3 = -90.3207887907066
x4 = 65.1880475619882
x5 = 40.0553063332699
x6 = 60.4756585816035
x7 = -35.3429173528852
x8 = 33.7721210260903
x9 = -22.776546738526
x10 = -66.7588438887831
x11 = -96.6039740978861
x12 = -71.4712328691678
x13 = 8.63937979737193
x14 = 14.9225651045515
x15 = -73.0420291959627
x16 = 73.0420291959627
x17 = -16.4933614313464
x18 = -84.037603483527
x19 = 66.7588438887831
x20 = -14.9225651045515
x21 = 90.3207887907066
x22 = 84.037603483527
x23 = 85.6083998103219
x24 = -65.1880475619882
x25 = -47.9092879672443
x26 = 71.4712328691678
x27 = 255.254403104171
x28 = 2584.745355741
x29 = -46.3384916404494
x30 = -3.92699081698724
x31 = 91.8915851175014
x32 = -27.4889357189107
x33 = -77.7544181763474
x34 = 52.621676947629
x35 = 104.457955731861
x36 = -98.174770424681
x37 = -29.0597320457056
x38 = -52.621676947629
x39 = -79.3252145031423
x40 = -58.9048622548086
x41 = -8.63937979737193
x42 = 46.3384916404494
x43 = -21.2057504117311
x44 = 47.9092879672443
x45 = 10.2101761241668
x46 = 39349.2333843756
x47 = 77.7544181763474
x48 = 96.6039740978861
x49 = 41.6261026600648
x50 = -10.2101761241668
x51 = 22.776546738526
x52 = 16.4933614313464
x53 = -91.8915851175014
x54 = -60.4756585816035
x55 = -41.6261026600648
x56 = 58.9048622548086
x57 = -54.1924732744239
x58 = 27.4889357189107
x59 = -40.0553063332699
x60 = 79.3252145031423
x61 = -33.7721210260903
x62 = 3.92699081698724
x63 = 54.1924732744239
x64 = 35.3429173528852
x65 = 29.0597320457056
x66 = 21.2057504117311
x67 = 2.35619449019234
x68 = -2.35619449019234
x69 = 98.174770424681
x69 = 98.174770424681