Concept understanding — Derivatives of Inverse Trigonometric Functions
Inverse trigonometric functions (sin−1x,cos−1x,tan−1x,cot−1x,sec−1x,cosec−1x) are multi-valued in general, so a principal branch (a restricted domain and range) is fixed for each before differentiating. Each derivative is found by treating y= (inverse trig function of x) as x= (trig function of y), differentiating implicitly with respect to y, and using a Pythagorean identity to express the result back in terms of x. The six standard results are: dxdsin−1x=1−x21, dxdcos−1x=−1−x21, dxdtan−1x=1+x21, dxdcot−1x=−1+x21, dxdsec−1x=xx2−11 (for x>1; sign flips for x<−1), and dxdcosec−1x=−xx2−11 (for x>1; sign flips for x<−1). When the argument is a function f(x) rather than pla …
Let s=2x, so 22x+1=2s2, and y=tan−1(1+2s2s). With N=s,D=1+2s2 (functions of x via s=2x): N′=sln2, and since D=1+2s2, D′=4s⋅sln2=4s2ln2. So N′D−ND′=sln2(1+2s2)−s⋅4s2ln2=sln2[(1+2s2)−4s2]=sln2(1−2s2). Also D2+N2=(1+2s2)2+s2=1+5s2+4s4=(1+4s2)(1+s2). So $\dfrac{dy}{dx}=\dfr …