Очень, очень нужно! Помогите
а) 10π+π/2<α<11π+π/2 π/2<α<π+π/2 <strong>π/2<α<3π/2</strong>
b) -20π-π/2<α<-20π+π/2 <strong>-π/2<α<+π/2</strong>