Answer
$y=-2x+2$
Work Step by Step
The tangent line at $x=1$ has slope $m=f^{\prime}(1)$
For $f^{\prime}(x)$, apply the Chain Rule and $\displaystyle \frac{d}{dx}[\sinh u]=(\cosh u)u^{\prime}$
$f(x)=\sinh(1-x^{2}),$
$f^{\prime}(x)=\cosh(1-x^{2})(-2x)$
$m=f^{\prime}(1)=\cosh(0)(-2)=1(-2)=-2$
Tangent line at $(1,0)$:
$y-y_{1}=m(x-x_{1})$
$y-0=-2(x-1)$
$y=-2x+2$