Question

sin(π-a) + cos(3π/2 -a ) / ctg(π/2 +a) - tg (π + a)

Answer 1

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Answer 2

$frac{sin( pi -a) + cos(3 pi -a )}{ctg (pi +a) - tg (pi + a)}$
          По формулам приведения

$frac{sin(a)-sin(a)}{-tg(a)-tg(a)} = 0$