Solving derivative- possible without quotient rule?

Persimmon
Messages
22
Reaction score
0

Homework Statement


find the following derivative
d/dx [g(x + 1)(√(2+ (x + 8)^(1/3))/(cos(tan(sin(tan(sin x))))]
at x = 0

Homework Equations





The Attempt at a Solution



I split the big long derivative into 3 functions:
a(x) = g(x + 1)
b(x) = √(2+ (x + 8)^(1/3))
c(x) = cos(tan(sin(tan(sin x))))

and got : (a'x*bx + b'x*ax)(cx)-c'x*px*qx)/cx^2
subbing in x = 0 that simplified into 2*g'(1)
but it was mentioned that it's possible to solve this without the quotient rule. I can't figure out how you would solve this derivative if you didn't use the quotient rule.
 
Physics news on Phys.org
Persimmon said:

Homework Statement


find the following derivative
d/dx [g(x + 1)(√(2+ (x + 8)^(1/3))/(cos(tan(sin(tan(sin x))))]
at x = 0

Homework Equations





The Attempt at a Solution



I split the big long derivative into 3 functions:
a(x) = g(x + 1)
b(x) = √(2+ (x + 8)^(1/3))
c(x) = cos(tan(sin(tan(sin x))))

and got : (a'x*bx + b'x*ax)(cx)-c'x*px*qx)/cx^2
subbing in x = 0 that simplified into 2*g'(1)
but it was mentioned that it's possible to solve this without the quotient rule. I can't figure out how you would solve this derivative if you didn't use the quotient rule.
Instead of dividing by cos(...), you can multiply by sec(...). That way you're set up to use the product rule.

BTW, your notation is not very helpful.
a'x*bx + b'x*ax)(cx)-c'x*px*qx)/cx^2
As written this looks like a' * x * b * x etc. To be clearer, write a'(x) * b(x) etc.
 
  • Like
Likes 1 person
Sorry for the unclear notation. I was trying to make it clearer so there wouldn't be endless brackets but I guess it's even more confusing that way. Thank you for your help!
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
Back
Top