If one line of the equation :
ax^3 +bx^2 y+cxy^2 +dy^3 =0
bisects the angle between the
the other two then prove
(3a+c)^2 (bc+2cd−3ad)=
(b+3d)^2 (bc+2ab−3ad) .
1) find P∈R[x] / P(sinx) =sin(2n+1)x
2) find the roots of P and degP
3) decompose (1/P) and prove that
((2n+1)/(sin(2n+1)x)) = Σ_(k=0) ^(2n) (((−1)^k cos(((kπ)/(2n+1))))/(sinx−sin (((kπ)/(2n+1)))))) .
let give A= ( cosθ −sinθ )
( sinθ cosθ )
1) calculate^t A. A .prove that A is inversible and find
A^(−1)
2) find A^n for n∈ N
3) developp (A +A^(−1) )^n then prove that
2^n cos^n θ = Σ_(k=0) ^n C_n ^k (n−2k)θ and
Σ_(k=0) ^n C_n ^n sin(n−2k)θ =0 .