The teacher will be very surprised to see your correct solution 😉
/x pi\ cos|- - --| = 0 \2 4 /
with the change of sign in 0
-pi x1 = ---- 2
3*pi x2 = ---- 2
x2 = 3*pi/2
sum
pi 3*pi - -- + ---- 2 2
=
pi
product
-pi 3*pi ----*---- 2 2
=
2 -3*pi ------ 4
-3*pi^2/4
x1 = 17.2787595947439
x2 = -14.1371669411541
x3 = -95.8185759344887
x4 = -146.084058391925
x5 = -26.7035375555132
x6 = 4.71238898038469
x7 = -246.615023306799
x8 = 23.5619449019235
x9 = 42.4115008234622
x10 = 36.1283155162826
x11 = 29.845130209103
x12 = 61.261056745001
x13 = 48.6946861306418
x14 = -7.85398163397448
x15 = -51.8362787842316
x16 = -76.9690200129499
x17 = -89.5353906273091
x18 = -39.2699081698724
x19 = 80.1106126665397
x20 = 67.5442420521806
x21 = -32.9867228626928
x22 = -20.4203522483337
x23 = -824.668071567321
x24 = -45.553093477052
x25 = -1.5707963267949
x26 = -70.6858347057703
x27 = -83.2522053201295
x28 = 98.9601685880785
x29 = -102.101761241668
x30 = 73.8274273593601
x31 = -58.1194640914112
x32 = 92.6769832808989
x33 = 54.9778714378214
x34 = 86.3937979737193
x35 = -64.4026493985908
x36 = 10.9955742875643
x36 = 10.9955742875643