Question

Подскажите как делать,пожалуйста. Номер 2)

Answer 1

   sint         1+cost        sin²t-(1-cos²t)     sin²t+cos²t-1
---------  -  -----------  =  ------------------- = ------------------  = 0
1-cost          sint            sint* (1-cost)          ......

Answer 2

$frac{sint}{1-cost} - frac{1+cost}{sint}= frac{sin^2t-(1-cost)(1+cost)}{(1-cost)sint} =\\= frac{sin^2t-(1-cos^2t)}{(1-cost)sint}= frac{sin^2t-sin^2t}{(1-cost)sint}= frac{0}{(1-cost)sint}=0$