Question

sin 15 grade ori cos 75 grade+cos patrat de 165 de grade

Answer 1

   
[tex]\displaystyle\\ \sin15^o \times \cos75+\cos^2 165^o =\\\\ =\sin15^o \times \sin(90-75)+(1-\sin^2 165^o) =\\\\ =\sin15^o \times \sin15+1-\sin^2 (180^o-165^o) =\\\\ =\underline{\sin^2 15^o}+1-\underline{\sin^2 15^o} = \boxed{\bf \texttt{\bf 1}}[/tex]

Answer 2

sin15°·cos75° +  cos² 165° = sin15°·sin(90°-75° ) +  cos² (180°-165°) =

sin²15° +cos²15° = 1