Given,csc x dx=csc x ·csc x + cot xcsc x + cot x dx=csc2x + csc x cot xcsc x + cot x dxu = csc x + cot xdu =-csc x cot x +-csc2x dxdx =du-csc x cot x - csc2x=csc2x + csc x cot xu⋅du-csc x cot x - csc2xcsc2x + csc x cot xu⋅du-csc x cot x + csc2x=-1u du=- In |u|+ C=- In|csc x + cot x|+ C
Problem 9 :
sin2 x dx
Solution :
Given,sin2 x dx=1 - cos 2x2 dx=12 1 - cos 2x dx=12dx -cos 2x dx=12x -sin 2x2+ C=12x -14 sin 2x + C
Problem 10 :
sin3 x dx
Solution :
Given,sin3 x dx=sin2 x ·sin x dx=1 - cos2x· sin x dxu = cos x , du =-sin x dxdx =-1sin x du=1 - u2· sin x ·-1sin x du=-1 - u2 du=-du -u2 du=-u +u33+ C=-cos x +cos3 x3+ C
Problem 11 :
tan3 x dx
Solution :
Given,tan3 x dx=sin3xcos3x dx=sin2xcos3x·sin x dx=1 - cos2xcos3 x·sin x dxu = cos xdu =-sin x dxdx =-dusin x=1 - u2u3·sin x ·-dusin x=-1u3-1u du=-u-3-1u du=--12u-2- In|u|=12u2+ In|u|=12cos2x+ In|cos x|+ C=12sec2x + In |cos x|+ C
Problem 12 :
sin 7x cos 3x dx
Solution :
Given,sin 7x cos 3x dxsin A cos B =12[sin (A + B)+ sin (A - B)]=12(sin (7x + 3x)+ sin (7x - 3x))dx=12 sin (10x)+ sin (4x) dx=12sin 10x + sin 4x dx=12sin 10x dx +sin 4x dx=12110(-cos 10x)+14(-cos 4x)=120(-cos10x)-18cos 4x=-120cos 10x -18cos 4x + C
Problem 13 :
sin 10x sin 4x dx
Solution :
Given,sin 10x sin 4x dxsin A sin B =12[cos (A - B)+ cos (A + B)]=12(cos (10x - 4x)+ cos (10x + 4x))dx=12 cos (6x)+ cos (14x)) dx=12cos 6x + cos 14x dx=12cos 6x dx +cos 14x dx=1216sin 6x +114sin 14x]=112sin 6x -128sin 14x=112sin 6x -128sin 14x + C