Question

HELP FAST PLEASE!!
Martin simplified the composed function f(x)=sin(arctan x). His work is shown below. Step 1: f(x)=sinA, where A=arctan x and x = tanA
Step 2: tanA= opp/adj=x/1
Step 3: hypotenuse= square root of 1^2-x^2= square root of 1-x^2
Step 4: sinA=opp/hyp=x/squareroot 1-x^2
In which step did Martin make is first error?

Answer 1

We will evaluate Martin's work step by step:
 Step 1: 
 f (x) = sinA,
 where
 A = arctan x
 and
 x = tanA
 step 1 it's OK
 Step 2: 
 tanA = opp / adj = x / 1
 step 2 it's OK
 Step 3: 
 hypotenuse = square root of 1 ^ 2-x ^ 2 = square root of 1-x ^ 2
 step 3 it's NOT OK
 The correct form in this case is:
 hypotenuse = square root of 1 ^ 2 + x ^ 2 = square root of 1 + x ^ 2
 Answer:
 Martin did make his first mistake in Step 3.