Question

соѕ40°+cos80°+cos160°
+cos240°= *
А. 0
В. 1
с. 1/2
D. -1/2
Plz answer me fast ​

Answer 1

Answer:

Answer is 1/2

Step-by-step explanation:

0.76 + 0.17 + (-0.93) + (-0.5)

0.93 - 1.43

0.5

That means 1/2 = 0.5

So 1/2

I THINK MY ANSWER IS CORRECT

If correct pls thank me

Answer 2

Answer:

Answer is -1/2

Step-by-step explanation:

cos40+cos89+cos160+cos240

= 2 cos (40+80)/2cos(40-80)/

2 cos (180-20)+cos(180+60)

[ cos C + cos D = 2 cos ( C + D)/2cos(C-D)/2]

= 2cos60.cos20+cos{(90×2)-20}+cos{(90×2)+60}

= 2×1/2cos20+(-cos20)+(-cos60)

[cos60=1/2,cos(180-A)=-cosA,

cos(180+A)= -cosA]

=cos20-cos20-1/2

= -1/2 answer