Question Number 79187 by john santu last updated on 23/Jan/20
$$\underset{\mathrm{0}} {\overset{\pi} {\int}}\:\frac{\mathrm{cos}\:\left({nx}\right)−\mathrm{cos}\:\left({n}\alpha\right)}{\mathrm{cos}\:\left({x}\right)−\mathrm{cos}\:\left(\alpha\right)}\:{dx} \\ $$