The 10' can be represented as (10/60)° = (1/6)° so:
$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\mathtt{75}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{1}}}{{\mathtt{6}}}}\right)} = {\mathtt{0.256\: \!008\: \!189\: \!722}}$$
.