Evaluate `lim_(xrarr(pi)/(2))(cosx)/(((pi)/(2)-x)).`

1.	Evaluate `lim_(xrarr(pi)/(2))(cosx)/(((pi)/(2)-x)).`
Answer» Put `(x-(pi)/(2))=y,` so that when `xto(pi)/(2)then tyto0.` `thereforelim_(xto(pi)/(2))(cosx)/(((pi)/(2)-x))=lim_(yto0)(cos((pi)/(2)+y))/(-y)=lim_(yto0)((-siny)/(-y))=lim_(yto0)(siny)/(y)=1.`

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