Solution :
The value of Sec 0 degrees is equal to 1.
Proof :
∠ A is made smaller and smaller in the right Δ ABC till it becomes zero. As ∠ A gets smaller and smaller the length of the side BC decreases. The point C gets closer to the point B and finally when ∠ A becomes very close to 0 degrees, AC becomes almost the same as AB, and BC gets very close to 0.
By using trigonometric formula,
Sec A = hypotenusebase = hb
AC is nearly becoming the same as AB.
Sec A = ACAB = ABAB = 1
Hence, sec0∘ = 1