Do you know any trick to solve trigonometric question that come in iitjee

yes there are many tricks to solve trigonometry questions......for example in cases like 

Tan(a+b+c)= or any sort of Ange's you can take the values of these angle on your own and match with the options for example take a=90 b=0 c=45 and solve.,

please tell some more tricks and direct formulas that are very useful for iitjee....................................................................................................................................................................................................................................