cos20+cos40+cos60+.....cos180
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Answer:
answer is 1
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Step-by-step explanation:
APPLY FORMULAE
ANGLES ARE IN AP MUST*
eg 20+40+60..........180
find n
n= 9 20/2=10
sin (nd/2) cos(a+(n-1)/2 d/2) / sin (d/2)
sin (90) cos (100) / sin 10
sin 90 cos (90+10) / sin 10
-sin 10/sin10
= -1
I HAVE TRIED TO GIVE EASIEST METHOD HOPE IT HELPS U
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