2cos(2011π-x)+4cos(2012π-x)+cos(1433π+x) svp

2cos (2010 pi + pi -x ) + 4 cos ( 2012pi -x) + cos ( 1432 pi +pi +x)

2010 pi = 1005 * 2pi = 0 ( car 2pi = 0)
2012pi  =1006* 2pi = 0
1432 pi =716 * 2 pi =0

2cos ( pi -x ) + 4 cos (  -x) + cos ( pi +x)

cos (pi - x) = -cos x          formules   du cours
cos ( -x)  = cos x
cos (pi + x) = - cos x

=> 2cos ( pi -x ) + 4 cos (  -x) + cos ( pi +x) 
= - 2cos x    + 4 cos x   - cos x

=   cos x