Here are the evaluations for the given limits:
1) Evaluate limx→0+xsinx
Step 1: Identify the indeterminate form.
As x→0+, x→0 and sinx→0. This is an indeterminate form of type 00.
Step 2: Use logarithms to convert to a product form.
Let y=xsinx. Then lny=ln(xsinx)=sinxlnx.
Now, we evaluate limx→0+lny=limx→0+sinxlnx.
This is an indeterminate form of type 0⋅(−∞).
Step 3: Rewrite the expression to apply L'Hôpital's Rule.
Rewrite sinxlnx as 1/sinxlnx=cscxlnx.
Now, as x→0+, lnx→−∞ and cscx→∞. This is an indeterminate form of type ∞−∞.
Step 4: Apply L'Hôpital's Rule.
limx→0+dxd(cscx)dxd(lnx)=limx→0+−cscxcotx1/x
=limx→0+x1⋅cosx−sinx⋅sinx
=limx→0+xcosx−sin2x
We can rewrite this as:
=limx→0+(−xsinx⋅cosxsinx)
=limx→0+(−xsinx⋅tanx)
Step 5: Evaluate the limit.
We know that limx→0+xsinx=1 and limx→0+tanx=0.
So, limx→0+lny=−(1⋅0)=0.
Step 6: Find the original limit.
Since limx→0+lny=0, then limx→0+y=e0=1.
The limit is 1.
2) Evaluate limx→0+(1+3x)1/(2x)
Step 1: Identify the indeterminate form.
As x→0+, 1+3x→1 and 2x1→∞. This is an indeterminate form of type 1∞.
Step 2: Use the standard limit definition of e.
Recall the definition: limu→0(1+u)1/u=e.
Let u=3x. As x→0+, u→0+.
Substitute u into the expression:
limu→0+(1+u)2(u/3)1
limu→0+(1+u)2u3
Step 3: Manipulate the exponent to match the definition of e.
limu→0+[(1+u)u1]23
Step 4: Evaluate the limit.
Using the property of limits for powers:
=[limu→0+(1+u)u1]23
=e23
The limit is e3/2.
3) Evaluate limx→∞(x2+x)1/lnx
Step 1: Identify the indeterminate form.
As x→∞, x2+x→∞ and lnx→∞, so lnx1→0. This is an indeterminate form of type ∞0.
Step 2: Use logarithms to convert to a product form.
Let y=(x2+x)1/lnx. Then lny=ln((x2+x)1/lnx)=lnx1ln(x2+x)=lnxln(x2+x).
Now, we evaluate limx→∞lny=limx→∞lnxln(x2+x).
As x→∞, ln(x2+x)→∞ and lnx→∞. This is an indeterminate form of type ∞∞.
Step 3: Apply L'Hôpital's Rule.
limx→∞dxd(lnx)dxd(ln(x2+x))=limx→∞x1x2+x2x+1
Step 4: Simplify the expression.
=limx→∞x2+x2x+1⋅x
=limx→∞x2+xx(2x+1)
=limx→∞x2+x2x2+x
Step 5: Evaluate the limit by dividing by the highest power of x in the denominator.
Divide the numerator and denominator by x2:
=limx→∞x2x2+x2xx22x2+x2x
=limx→∞1+x12+x1
As x→∞, x1→0.
=1+02+0=2
So, limx→∞lny=2.
Step 6: Find the original limit.
Since limx→∞lny=2, then limx→∞y=e2.
The limit is e2.
That's 2 down. 3 left today — send the next one.