Prove the following question.
∫π20sin3 x dx=23.
Let I = ∫π20sin3 x dx=∫π20sin2 x. sin x dx =∫π20(1−cos2x)sin x dx (∵ sin2x=1−cos2x)Put,cos x=t ⇒−sin x dx=dtWhen x=0⇒ t=cos 0=1,when x=π2=0∴ I=∫π20(1−cos2x)sin x dx=∫01(1−t2)(−dt)=−[t−t33]01=−{(0−0)−(1−13)}=23. Hence proved.