Find the derivative of f(t)=t2+1⋅cos(t)f(t) = \sqrt{t^2+1} \cdot \cos(t)f(t)=t2+1⋅cos(t).
tcostt2+1−t2+1sint\frac{t \cos t}{\sqrt{t^2+1}} - \sqrt{t^2+1} \sin tt2+1tcost−t2+1sint
tt2+1cost−t2+1sint\frac{t}{\sqrt{t^2+1}} \cos t - \sqrt{t^2+1} \sin tt2+1tcost−t2+1sint
12t2+1cost−t2+1sint\frac{1}{2\sqrt{t^2+1}} \cos t - \sqrt{t^2+1} \sin t2t2+11cost−t2+1sint
tcostt2+1+t2+1sint\frac{t \cos t}{\sqrt{t^2+1}} + \sqrt{t^2+1} \sin tt2+1tcost+t2+1sint