LinkBack URL
About LinkBacks
I am posting this on behalf of vc15ao4 who seems to have problems posting.
Originally Posted by vc15ao4
i, and a lot of other people on this site, write the "long looking s" as "int" for integral--that is if we're not using LaTex.1) Evaluate the integral: (long looking s?) e^(ax+b)dx
there's a shortcut to find the integral of a function like this, that is a function where we have e raised to some polynomial in x with the highest power of x being 1, but its probably dangerous telling you that at this point, so let's do this the proper way, by substitution.
int{e^(ax+b)}dx
let u = ax + b
=> du = a dx ...........took the derivative of ax + b with respect to x
=> 1/a du = dx
so our integral becomes:
(1/a)*int{e^u}du
= (1/a)e^u + C
= (1/a)e^(ax + b) + C
see the diagram below called areaquestion2, the shaded region is the region we want the area of.2) Use a graphing utility to graph f(x)= 4-x/x. Then determine the area of the region in the first quadrant bounded by f, the xaxis, and x=1.
we know that one of the limits of integration is x = 1, but what's the other? we need to find where (4 - x)/x cuts the x-axis. in other words, we want the point(s) where
y = (4 - x)/x intersects y = 0
=> (4 - x)/x = 0
=> 4 - x = 0
=> x = 4
so our limits of integration are 1 to 4
so A = int{(4 - x)/x}dx evaluated between 1 and 4
int{(4 - x)/x}dx
= int{4/x - 1}dx
= 4ln(x) - x + C evaluated between 1 and 4
=> A = 4ln(4) - 4 - 4ln(1) + 1
=> A = 4ln(4) - 3 ................ln(1) = 0
i'm almost certain i've done this exact problem on this site before...o well3) Use a graphing utility as an aid to sketch the region bounded by the fuction f(x)= 1/(square roof of 9-x^2) , the x axis, and the lines x=1, and x=2. Then calculate the area of the region
by the way, it's "squareroot" not "square roof," but i guess that's an honest mistake
see the diagram below called areaquestion3, the shaded region is the part we want the area of
our limits of integration are obviously x = 1...2, so now
A = int{1/sqrt(9 - x^2)}dx
let's simplify this a bit, factor out the 9 out of the bottom of the squareroot, you'll see why
=> A = int{1/sqrt[9(1 - (x^2)/9]}dx ...........simplify a bit more
=> A = int{1/sqrt[9(1 - (x/3)^2)]}dx
=> A = int{1/[sqrt(9) * sqrt(1 - (x/3)^2)}dx ........you should be able to see it now, i was going for arcsine
=> A = (1/3)*int{1/sqrt(1 - (x/3)^2)}dx ..........i changed 1/sqrt(9) to 1/3 and factored it out
again, there's a shortcut here, but let's be proper
now let u = x/3
=> du = 1/3 dx
=> 3 du = dx
so our integral becomes:
(1/3)(3)int{1/sqrt(1 - u^2)}du
= arcsin(u) + C
= arcsin(x/3) + C .........now we evaluate between our limits
=> A = arcsin(2/3) - arcsin(1/3)
