(a)Prove that∫2a0f(x)dx=2∫a0f(X)dx,if f(2a−x)=f(x) and evaluate∫2π0cos5xdx
if f(2a−x)=−f(x)
(b) Find the values of a and b such that the function defined by
f(x)=⎧⎪⎨⎪⎩5,if x≤2ax+bif 2<x<10 is a continous function21,if x≥10
(a)∫2a0f(x)dx=∫a0f(x)dx+∫2aaf(x)dx For derivationsLetI1=∫2a0f(x) dx For ProblemPut 2a−x=t⇒x=2a−t dx=−dtx=a⇒t=a,x=2a⇒t=0⇒I=∫0af(2a−t)(−dt)=∫0af(2a−x)dx(b)f(x)is continuous⇒ltx→2−f(x)=ltx→2+andltx→10−f(x)ltx→10+f(x)⇒5=2a+b and 10a+b=21⇒a=2,b=1