Let F(x) be an indefinite integral of sin² x. STATEMENT 1 : The function F(x) satisfies F(x+π) = F(x) for all real x. because STATEMENT 2 : sin²(x+π) = sin² x for all real x.
F(x)=∫sin2xdx
Statement 1: F(x+π)=F(x) ∀x∈R
Statement 2: sin2(x+π)=sin2x ∀x∈R
To find: truth of both statements, and whether (2) explains (1)
1. find F(x)=∫sin2xdx
2. check Statement 2: sin2(x+π)
3. check Statement 1: compare F(x+π) with F(x)
F′(x)=sin2x,F(x)=∫sin2xdx
sin2x=21−cos2x
F(x)=21∫(1−cos2x)dx=2x−4sin2x+C
sin(x+π)=−sinx⇒sin2(x+π)=sin2x⇒Statement 2 is TRUE
F(x+π)=2x+π−4sin(2x+2π)+C
=2x+2π−4sin2x+C=F(x)+2π
F(x+π)−F(x)=2π=0⇒Statement 1 is FALSE
Mean of sin2x over a period=21=0⇒a linear term 2x survives
Statement 1 False, Statement 2 True⇒(4)
Answer: (4)