Question

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10=) 2 cos^2 x - sen x -1 =0

Answer 1

Resposta:

2cos²(x)-sen(x) -1 =0

2*(1-sen²(x)-sen(x)-1=0

2-2sen²(x)-sen(x)-1=0

-2sen²(x)-sen(x)+1=0

2sen²(x)+sen(x)-1=0

Fazendo y=sen(x)

2y²+y-1=0

y'=[-1+√(1+8)]/4 =(-1+3)/4=1/2

y''=[-1-√(1+8)]/4 =(-1-3)/4=-1

Se y=1/2=sen(x) ==> x=pi/6  , x=pi-pi/6=5pi/6

Se y=-1=sen(x) ==>x=3pi/2