Question 1011

Definite Integrals: Areas and Volumes
2011 Paper 1 Question 5 Variant

Question

It is given that f(x)=1−x.{f(x)=1 - x.}
(i)
On separate diagrams, sketch the graphs of y=f(∣x∣){y=f(|x|)} and y=∣f(x)∣,{y=|f(x)|,} giving the coordinates of any points where the graphs meet the x-{x\textrm{-}} and y-{y\textrm{-}}axes. You should label the graphs clearly.
[3]
(ii)
State the set of values of x{x} for which
f(∣x∣)=∣f(x)∣.f(|x|)=|f(x)|.
[1]
(iii)
Find the exact value of the constant a{a} for which
∫−1212f(∣x∣)  dx=∫12a∣f(x)∣  dx.\int_{- \frac{1}{2}}^{\frac{1}{2}} f(|x|) \; \mathrm{d}x = \int_{\frac{1}{2}}^a |f(x)| \; \mathrm{d}x.
[3]

Answer