Cot^2 x-csc^2 x=-1 for all values of x

Ihave trouble finding the nth term of a linear sequence

See attachment below and find the equivalent of tan(∠qsr)

Awoman has 14 different shirts: 10 white shirts and 4 red shirts. if she randomly chooses 2 shirts to take with her on vacation, then what is the probability that she will choose two white shirts? show your answer in fraction and percent, round to the nearest whole percent.