Cassie simplified the composed function f left parenthesis x right parenthesis equals cotangent left parenthesis arc sine x right parenthesis. Her work is shown below. Step 1: f left parenthesis x right parenthesis equals cotangent upper A, where A = arcsin x and x = sin A
Step 2: sine upper A equals Start Fraction opposite over hypotenuse End Fraction equals Start Fraction x over 1 End Fraction
Step 3: adjacent equals Start Root 1 squared minus x squared End Root equals Start Root 1 minus x squared End Root
Step 4: cotangent upper A equals Start Fraction opposite over adjacent End Fraction equals Start Fraction x over Start Root 1 minus x squared End Root End Fraction

In which step did Cassie make her first error?
A. step 1
B. step 2
C. step 3
D. step 4
E. She did not make an error.