grandes-ecoles 2010 QI.A.1

grandes-ecoles · France · centrale-maths1__pc Addition & Double Angle Formulae Trigonometric Identity Proof or Derivation
For every integer $n \in \mathbb{N}$, we set $F_n(x) = \cos(n \arccos x)$.
a) Show that the functions $F_n$ are defined on the same domain $D$ which should be specified.
b) Calculate $F_1(x), F_2(x)$ and $F_3(x)$ for all $x \in D$.
c) Calculate $F_n(1), F_n(0)$ and $F_n(-1)$ for all $n \in \mathbb{N}$.
d) Specify the parity properties of $F_n$ as a function of $n$.
For every integer $n \in \mathbb{N}$, we set $F_n(x) = \cos(n \arccos x)$.

a) Show that the functions $F_n$ are defined on the same domain $D$ which should be specified.

b) Calculate $F_1(x), F_2(x)$ and $F_3(x)$ for all $x \in D$.

c) Calculate $F_n(1), F_n(0)$ and $F_n(-1)$ for all $n \in \mathbb{N}$.

d) Specify the parity properties of $F_n$ as a function of $n$.