Question

Folosind formulele sin(180-x)=sinx , cos(180-x)= -cosx sa se calculeze:
a) sin 135(de grade)
b) cos 125
c) sin 150
d) cos120

Answer 1

 pe sin 135 il scriu ca sin(180-45)=sin180cos45-ssin45cos180(formula sin(a-b)....rezolv inlocuind valorile        


sin150=sin (180-30)=sin180cos30+sin30 cos 180 

 cos 120=cos(180-60)=cos180cos60-sin180sin60

Answer 2

a) sin (135)=sin(180-135)=sin(45)=$\frac{ \sqrt{2} }{2}$
b) cos (125)=-cos(180-125)=-cos(55)
c)sin(150)=sin(180-150)=sin30=0.5
d)cos(120)=-cos(180-120)=-cos60=-0.5