To solve the Trigonometry's MCQs, first of all you need to learn all the formulae and aproach and ofcourse start practicing. 

For your reference, click on the following link, so many MCQs are solved and explained here: 

https://www.youtube.com/watch?v=HdB63fiud6I&list=PLCzaIJYXP5YfJbWwJCFw0jKFp-BWHY4Jo