Question

(secA-tanA)^2=1-sinA÷1+sinA

Answer 1

(1-sinA)/(1+sinA)

=(1-sinA)(1-sinA)/(1+sinA)(1-sinA)

=(1-sinA)^2/(1-sin^2A)

=(1-sinA)^2/cos^2A

={(1-sinA)/cosA}^2

={(1/cosA)-(sinA/cosA)}^2

={secA-tanA}^2..........proved