(iii) y = − 3 , y = 3

(iii) y = − , y = (iv) y − , x = − EXERCISE . ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) Exercise . . (i) . . (i) . (ii) . (iii) . . (i) x − (ii) − x (iii) x + . (i) . π cm , (ii) . cm (iii) . % . (i) Volume decreases by π cm (ii) Surface area decreases by π cm . % Exercise . . (i) ) ( dx (ii) (iii) e [( )cos( sin( )] . (i) . (ii) . . (i) ∆ f = , df = . (ii) ∆ f = , df = . . .0013029 . (i) π cm (ii) π % . π mm . . π mm . . (i)  words (ii)  word . . π cm , . % . cm , . cm Exercise . . (i) , − (ii) , − (iii) , , (iv) e ) − . x x y y x z , 6yz . z z . (i) e y + , y , xe y , e y + (ii) (iii) , cos x , , . (i) (ii) , − , Keeping y constant and increasing x increases profit. Answers Exercise . . . − . y dx y dy + −+     . z dx z dy x dz