Concept:Differentiate an inverse trigonometric function using the chain rule.Explanation:Let u=25+x225−x2, so y=sin−1u.Then y′=1−u2u′.Using the quotient rule,u′=(25+x2)2(−2x)(25+x2)−(25−x2)(2x)This simplifies tou′=(25+x2)2−100x.Now compute the denominator:1−u2=1−(25+x225−x2)2=25+x210∣x∣.At x=1, u′=262−100 and 1−u2=2610.Therefore,y′(1)=10/26−100/262=−135.Answer:−135 (Option A).