Recent content by LRJ85

To all the civil/mechanical uni. grads out there, So after u have completed your Bachelor's degree in civil/mechanical engineering and u work for 4 years as an assistant engineer, can u apply to take the FE/FS exam to become a professional engineer? The total fees (registration + exam) is...

This diff. eqn is of the form a \frac{d^3x}{dt^3} + b \frac{d^2x}{dt^2} + c \frac{dx}{dt} + d = f(t) where a,b,c and d are numeric constants. The solution to this is the same as that for 2nd order linear diff. eqns with constant coefficients, provided that f(t) = 0. So we have...

I tink what hawaii meant was to find the solution to the diff. eqn 3x^2 \frac{d^2y}{dx^2} - x \frac{dy}{dx} + y = 0 at the point xo = 0. After looking through the "Series solution of 2nd Order Linear Equations" in thread #47 written by ExtravagantDreams, i realize that the above diff. eqn can...

Ok when u multiply the partial fraction identity by their common denominator, u get u^2 = (A+C)u^3 + (B+D+(C-A)\sqrt{2})u^2 + (A+C+(D-B)\sqrt{2})u + B + D . Compare coefficients of descending powers of u, u get A+C =0, B+D+(C-A)\sqrt{2}=1, A+C+(D-B)\sqrt{2}=0 and B+D=0. Sub. eqn 1 into eqn 3, u...

Yes, partial fractions will definitely work. The original integral is \int \sqrt{\tan x} dx. After letting tan x = u², u convert it to 2\int \frac{u^2}{1+u^4} du. Complete the square at the bottom to get (u²+1)²-2u² = (u^2-u\sqrt{2}+1)(u^2+u\sqrt{2}+1). Your integral becomes \int...