Question

Cum sa rezolv asta ????

Answer 1

$sin(\frac{\pi}{2} +x)*sinx+ cos(\frac{\pi}{2} +x)*cosx= cosx*sinx- sinx*cosx=0$

Answer 2

$\it Notez\ \ \dfrac{\pi}{2} +x = t,\ iar\ membrul\ st\^{a}ng\ al \ expresiei\ \ devine: \\ \\ \\ E = sintsinx+costcosx = costcosx+sintsinx = cos(t+x)$

Revenim asupra notației :

$\it E= cos\left(\dfrac{\pi}{2}+x-x\right) = cos\dfrac{\pi}{2} =0$