The equation of normal to the curve y=cos x at origin is

To find normal we have to find slope of that normal at $(0,1).$

$y\text{'}\; =\; -sinx$

$slope\; of\; the\; normal\; is\; \$m\_\{slope\}\; =\; \backslash frac\{1\}\{-\; sinx\}|\_\{x=0\}\; =\; \backslash infty\$$

$Equation\; of\; normal\; is\; \$y\; -\; 0\; =\; m\_\{normal\}\; (x-0)\; \$$

$Since\; \$\; m\_\{normal\}\; =\; \backslash infty\$$

$Equation\; of\; normal\; is\; x\; =\; 0.$