Here's the question you clicked on:
dinainjune
lim (tan a - tan b) / 1+(1-a/b)tan a x tan b- a/b a->b
lim (tan a - tan b) / (1+(1-a/b)tan a x tan b- a/b) a->b
the answer is -b but how can I write equation on this site? Anyway, you can either use the L'hospital rule or this formula: tan(a-b)=(tana-tanb)/(1+tanatanb)