Question

y = 3/8 (x) + 3/8 sin x cos x + 1/4 cos^3(x)sin x find dy/dx

Answer 1

Answer:

3(cosx+sinx)−2(cos

3

x+sin

3

x)=8

⇒3cosx+3sinx−2cosx(1−sin

2

x)−2sinx(1−cos

2

x)=8

⇒cosx+sinx+2cosx.sinx(sinx+cosx)=8

⇒(cosx+sinx)(1+2cosx.sinx)=8

⇒(cosx+sinx)(sin

2

x+cos

2

x+2cosx.sinx)=8

⇒(cosx+sinx)

3

=8⇒cosx+sinx=2

but we know, sinx+cosx≤

2