In a right angled triangle ABC, if C is the right angle, then -
sin A = sec B
tan A = cosec B
cot A= sec B
sec A = tan B
cos A = sin B
If ∠C is the right angle in the Δ, then, A + B = 900 ⇒ A = 900- B
Try taking sin, tan and sec on both sides and get the answer.