Finding the value of tan(-945 degree)

method 1:
tan( - 945o)
= tan( - 3 × 360o + 135o)
= tan(135o)
= tan(180o - 45o)
= [sin(180o - 45o)]/[cos(180o - 45o)]
= [sin(45o)]/[-cos(45o)]
= -1
finding the value of tan(-945 degree)
formula used:
tan(a) = sin(a)/cos(a)
sin(180o - a) = sin(a)
cos(180o - a) = - cos(a)
when a = 45o, sin(a) = cos(a) = (square root of 2)/2
Method 2:
tan( - 945o)
= tan( -2 × 360o - 225o)
= tan( - 225o)
= tan( - (180o + 45o))
= [sin( - (180o + 45o))]/[cos( - (180o + 45o))]
= [- sin(180o + 45o)]/[cos(180o + 45o)]
= -[-(sin(45o)]/[-(cos(45o)]
= -1
finding the value of tan(-945 degree).
Formula used:
tan(a) = sin(a)/cos(a)
sin(-a) = - sin(a)
cos(-a) = cos(a)
sin(180o + a) = - sin(a)
cos(180o + a) = - cos(a)