If among all other memory requirements you have to know the integrals of sec(x) and sec^3(x) in a test ... Where does memorizing trig integrals end? 😬 ... then I guess I fail his class too. 😢 Lucky for me I'm not in integral Calculus and have a long list of Integral cheat sheet trig formulas of CRC tables to avoid that problem on my job!! 😂
I used the sustitution sen^2(theta)=1/(x+2), obtaining: cosec(theta)=sqr(x+2) and cotan(theta)=sqr(x+1). My integral was: (2cosec(theta)-2cosec^3(theta)) I had a equivalent result: ln|sqr(x+2)-sqr(x+1)|+sqr((x+2)(x+1))
(x+1)/(x+2) = u^2 This substitution lead us to integrating rational function without any secants After substitution proposed by me integration by parts will simplify partial fraction decomposition
The first thing i thought wheb i saw that integral was to immediately put x+1 = tan^2(u), then the top simplifies, the bottom turns to sec and simplifies, so youve got the integral of sin(u) * dx/du du
To be honest, I don’t know why am I continuing to learning integration math more… I think I’ve found it funny and interesting since my hight school. So, for last question in the video, we actually can get rid of absolute value inside the natural logarithm, cause inside we have a sum of two square roots, which is always greater than zero, so we don’t need absolute value. But… Is it a mistake to just leave it here?
Wolfram Alpha gives a very different result. Looks like your result only works for x > -1, so only for the real numbers. If you want complex solution, your way doesn't work.
@@niloneto1608Yes, my friend. When you see a problem, think of never dividing by zero. X can approach -2 but never reaches it. X is real by definition.
The function is undefined at x = -2 and is 0 at x = -1, but x < -2 and -2 < x < -1 can be calculated. The results for x < -2 are complex numbers, but they are still possible. And according to Wolfram Alpha, the integral CAN be calculated, so that these values are included.
