1-2cos^2b/cosb+sinb=? объясните плиз

[latex] \frac{1-2cos^2 \beta }{cos \beta +sin \beta }= \frac{(1-cos^2 \beta)-cos^2 \beta }{cos \beta +sin \beta }= \frac{(sin^2 \beta)-cos^2 \beta }{cos \beta +sin \beta }=[/latex] =[latex]\frac{(sin \beta-cos \beta)(sin \beta+cos \beta) }{cos \beta +sin \beta }=sin \beta-cos \beta[/latex]