sin^2x & cos^2x (1 Viewer)

[Ryuu-jin-jakka]

Primitive function of
a) 3sin^2 2x/5
b) sin^3 xdx <---- use substitution right???

 

[GUSSSSSSSSSSSSS]

(a) same as last trigonometry thread u posted, convert (sinx)^2 to (1/2)(cos2x -1)

(b) yea!!

 

[Ryuu-jin-jakka]

Qb is easy
Can someone show me the working out for a)
thanks!

 

[Timothy.Siu]

a) 3sin^2 2x/5=3/2 (cos 4x/5-1)
primtive, 3/2(5/4 sin 4x/5-x)+C

b) sin^3 xdx
S sin^3 xdx=Ssinx(1-cos^2x)dx=S(sinx-cos^2 xsinx)dx=-cosx+cos^3 x/3+C

 

[Ryuu-jin-jakka]

is it suppose to be 3/2(4/5cos4x/5-x)+c???
or like above, if so why do you flip the 4/5???

I understand now, got it p