Question

4 COS^2x + senx-1=0 (Ec)

Answer 1

cos²x=1-sen²x

4(1-sen²x)+senx-1=0
4-4sen²x+senx-1=0
4sen²x-senx-3 =0
 4senx          3
 senx           -1

(4senx+3)(senx-1)=0

senx =-3/4  ∨ senx=1

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