Concept:The expression is simplified using standard trigonometric identities, primarily secA=cosA1, tanA=cosAsinA, and 1−sin2A=cos2A.Explanation:Start with the given expression: (secA+tanA)(1−sinA).Substitute secA=cosA1 and tanA=cosAsinA.Then the expression becomes (cosA1+cosAsinA)(1−sinA).Combine the terms inside the brackets: cosA1+sinA.Now multiply by (1−sinA): cosA(1+sinA)(1−sinA).Use the algebraic identity (a+b)(a−b)=a2−b2: (1+sinA)(1−sinA)=1−sin2A.So the expression becomes cosA1−sin2A.Apply the identity 1−sin2A=cos2A: cosAcos2A.Cancel cosA in the numerator and denominator to get cosA.Thus, (secA+tanA)(1−sinA)=cosA.