I only memorized these trigonometric differential identities :(adsbygoogle = window.adsbygoogle || []).push({});

`sin(x) = cos(x)

`cos(x) = -sin(x)

because I can convert tan(x) to sin(x) / cos(x) and

sec(x) to 1 / cos(x) .. etc

And there is no need to memorize some integral identities such as :

∫ sin(x) dx = -cos(x) + C

∫ cos(x) dx = sin(x) + C

because I memorized

`sin(x) = cos(x)

`cos(x) = -sin(x)

But these identities seem inevitable to memorize:

∫ sec^2(x) dx = tan(x) + C

∫ cosec^2(x) dx = -cot(x) + C

∫ sec(x)tan(x) dx = sec(x) + C

∫ cosec(x)cot(x) dx = -cosec(x) + C

For example

∫ sec^2(x) dx = tan(x) + C

First I tried to convert sec^2(x) to 1 / cos^2(x)

∫ sec^2(x) dx = ∫ (1 / cos^2(x)) dx

And that's where I'm stuck.

It looks impossible to proceed anymore without memorizing a trigonometric differential identity

`tan(x) = sec^2(x)

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Should I memorize all these trigonometric integrals?

Tags:

**Physics Forums | Science Articles, Homework Help, Discussion**