Angle of measure 90°
: Let m∠XOA = 90°
Its terminal arm (ray OA) intersects the standard, unit circle at
P(0, 1).
∴ x = 0 and y = 1
sin 90° = y = 1
cos 90° = x = 0
tan 90° = x/y = 1/0, which is not defined
cosec 90° = 1/y = 1/1= 1
sec 90° = 1/x = 1/0, which is not defined
cot 90° = x/y = 0/1 =0
