Chilukuri Sai KartikApproved Tutor Answer14 Years agoDear Nitin, Given that SecA+TanA=x------ Eq.1 We know that Sec2A-Tan2A=1 This is of the form a2-b2=(a+b)(a-b) So (SecA-TanA)(SecA+TanA)=1 SecA-TanA=1/x {From eq.1} Lets consider this as Eq.2 Now adding Eq.1 and Eq.2, we get 2SecA=x+1/x Hence SecA=(x+1/x)/2 So SecA=(x2+1)/2x All the best! Plz approve my answer if you are satisfied.