Let a function f(x) defined on the set of all real numbers satisfy
f(x)=xsin(πx)for x∈[0,2],
and
f(x)=2f(x−2)for all real x.
Consider the region enclosed by the curve y=f(x), the line
y=21012(x−2026),
and the two vertical lines x=2026 and x=2027.The area of this region is equal to
21012(p+πq+πr3),
for some rational numbers p,q,r.Find the value of 2028⋅p⋅q⋅r.oindent
Ground Truth
1352
Execution Trace
Reasoning Process
[THOUGHT]
To solve this problem, we need to find the area of the region enclosed by the curve y=f(x), the line y=21012(x−2026), and the vertical lines x=2026 and x=2027.
Understand the function f(x):
For x∈[0,2], f(x)=xsin(πx).
For other x, f(x)=2f(x−2). This means f(x) is defined recursively, scaling by 2 every 2 units.
Find f(x) for x∈[2026,2027]:
Since f(x) is defined recursively, we can express f(x) in terms of f(x−2k) where x−2k∈[0,2].
For x∈[2026,2027], let x=2026+t where t∈[0,1].
Then, x−2×1013=2026+t−2026=t, so f(x)=21013f(t)=21013tsin(πt).
Set up the integral for the area:
The area is the integral of the difference between the line and the curve from x=2026 to x=2027.
The line is y=21012(x−2026)=21012t (where t=x−2026).
The curve is y=21013tsin(πt).
The difference is 21012t−21013tsin(πt)=21012t(1−2sin(πt)).
Compute the integral:
The area A is:
A=∫0121012t(1−2sin(πt))dt
This can be split into two integrals:
A=21012(∫01tdt−2∫01tsin(πt)dt)
The first integral is straightforward:
∫01tdt=21
The second integral requires integration by parts: