cos(pi/2-x)=0

с изменением знака при 0

Получим:
$$cos{left (- x + frac{pi}{2} right )} = 0$$
Это ур-ние преобразуется в
$$x = 2 pi n + {asin}{left (0 right )}$$
$$x = 2 pi n – {asin}{left (0 right )} + pi$$
Или
$$x = 2 pi n$$
$$x = 2 pi n + pi$$
, где n – любое целое число

x2 = pi

x1 = -94.2477796077000

x2 = 31.4159265359000

x3 = 81.6814089933000

x4 = 84.8230016469000

x5 = -53.4070751110000

x6 = 65.9734457254000

x7 = 3.14159265359000

x8 = 15.7079632679000

x9 = 100.530964915000

x10 = 50.2654824574000

x11 = -3.14159265359000

x12 = 40.8407044967000

x13 = -59.6902604182000

x14 = 97.3893722613000

x15 = 78.5398163397000

x16 = -25.1327412287000

x17 = -43.9822971503000

x18 = 25.1327412287000

x19 = -81.6814089933000

x20 = -91.1061869541000

x21 = 87.9645943005000

x22 = 69.1150383790000

x23 = -34.5575191895000

x24 = 28.2743338823000

x25 = -31.4159265359000

x26 = 37.6991118431000

x27 = -28.2743338823000

x28 = 72.2566310326000

x29 = 56.5486677646000

x30 = -75.3982236862000

x31 = -69.1150383790000

x32 = -6.28318530718000

x33 = -9.42477796077000

x34 = 6.28318530718000

x35 = 75.3982236862000

x36 = -65.9734457254000

x37 = -87.9645943005000

x38 = -72.2566310326000

x39 = 18.8495559215000

x40 = -267.035375555000

x41 = -84.8230016469000

x42 = 9.42477796077000

x43 = -50.2654824574000

x44 = -56.5486677646000

x45 = -232.477856366000

x46 = -2642.07942167000

x47 = 91.1061869541000

x48 = 59.6902604182000

x49 = -47.1238898038000

x50 = 12.5663706144000

x51 = -62.8318530718000

x52 = 62.8318530718000

x53 = -18.8495559215000

x54 = -12.5663706144000

x55 = -37.6991118431000

x56 = -97.3893722613000

x57 = 94.2477796077000

x58 = 34.5575191895000

x59 = -21.9911485751000

x60 = 21.9911485751000

x61 = -100.530964915000

x62 = 53.4070751110000

x63 = -113.097335529000

x64 = -78.5398163397000

x65 = 0.0

x66 = 43.9822971503000

x67 = -40.8407044967000

x68 = -15.7079632679000

x69 = 47.1238898038000