Stabiliți valoarea de adevar a propozitiei:sin π/2 × cos -π/2>0
A F

cos (-π/2) =cosπ/2=0
deci produsul e exact 0
deci F

[tex]\sin \left(\frac{\pi }{2}\right)\times \cos \left(-\frac{\pi }{2}\right) \\ \\ \cos \left(-x\right)=\cos \left(x\right) \\ \\ \cos \left(-\frac{\pi }{2}\right)=\cos \left(\frac{\pi }{2}\right) \\ \\ =\sin \left(\frac{\pi }{2}\right)\times \cos \left(\frac{\pi }{2}\right) \\ \\ \sin \left(\frac{\pi }{2}\right)=1 \\ \\ \cos \left(\frac{\pi }{2}\right)=0 \\ \\ =1\times \:0 \\ \\ =0 ( FALS)[/tex]