Question

1/1+cosa+1/1-cosa=
Помогите пожалуйста решить

Answer 1

$\frac{1}{1+cos(a)} + \frac{1}{1-cos(a)} = \frac{1-cos(a)+1+cos(a)}{(1+cos(a))(1-cos(a))}= \frac{2}{1-cos^2(a)} \\sin^2(a)+cos^2(a)=1\\sin^2(a)=1-cos^2(a)=\ \textgreater \ \\=\ \textgreater \ \frac{2}{sin^2(a)}$