Find the value of sec (2100 degrees )

ans -sec(120°)

sol: sec(2100°) =sec(11π+120°) [1]

in even multiples of π/2 we change sec to sec therefore [1] can be written as
[sign to be determined] sec(120°)
origlally it was sec also 11π+ some thing would mean 10π+π+120°
even comes to zero by rotating in circle which means originally it was sec π+ 120 3rd quad in which sec is negative so sign is negative
- sec(120°)