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cos3x+cos2x=0 sa se rezolve multimea solutiilor urm. ecuatii

Răspuns :

2 cos (3x+2x)/2cos(3x-2x)/2=0
2cos5x/2cosx/2=0
cos5x/2=0, 5x/2=+-arccos 0+2kπ=+-π/2+2kπ, k∈Z
x=+-π/5+4kπ/5, k∈Z
cosx/2=0, x=+-π+4kπ