Question

tan20 + tan 40 + tan 60 +....tan180

Answer 1

hint : tan180 = 0
tan160 = tan(180-20) = - tan20
tan140 = tan(180-40) = - tan40
tan120 = tan(180-60) = - tan60
tan100 = tan(180-80) = - tan80

Answer 2

THANKS

Answer 3

well, if u subtitute the values in my hint their sum be
tan20+tan40+tan60+tan80+tan100+tan120+tan140+tan160+tan180
= tan20+tan40+tan60+tan80-tan80-tan60-tan40-tan20+0
= (tan20-tan20)+(tan40-tan40)+(tan60-tan60)+(tan80-tan80)+0
= 0