Question

Monter que
cos2 30grade +cos2 60grade + cos2 45grade=1,5

Answer 1

 cos 30 =√3/3*2+2*1/2+2*√2/2=1.5
2√3/2+1+2√2=1.5 aducel la acelasi numitor comun
numitorul comun este2√3+
2+4√2/2=1.5
8√5/2=1.5 se simplifica cu 2
4√5=1.5

Answer 2

   
[tex]\boxed{cos\,60^o = sin(90^o - 60^o)=sin \,30^o} \\ \\ cos^230^o + cos^260^o + cos^245^o = \\ = \underbrace{cos^230^o + sin^230^o}_{=1} + (~\underbrace{cos45^o}_{= \frac{ \sqrt{2}}{2} }~)^2 = \\ \\ = 1 + \left( \frac{ \sqrt{2} }{2} \right)^2 = 1 + \frac{2}{4} =1 + \frac{1}{2} = \frac{3}{2} = \boxed{\boxed{1,5}}[/tex]