please answer this question
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Given Equation is cos 20 + cos 100 + cos 140 can be written as
Cos 140 + cos 100 + cos 20
We know that cos a + cos b = 2 cos (a + b)/2 cos (a - b)/2
2 cos (140 + 100)/2 * cos (140 - 100)/2+ cos 20
2 cos (240/2) * cos(40/2) + cos 20
2 cos 120 * cos 20 + cos 20
2 * (-1/2) * cos 20 + cos 20
-cos 20 + cos 20
= 0.
Hope this helps!
Cos 140 + cos 100 + cos 20
We know that cos a + cos b = 2 cos (a + b)/2 cos (a - b)/2
2 cos (140 + 100)/2 * cos (140 - 100)/2+ cos 20
2 cos (240/2) * cos(40/2) + cos 20
2 cos 120 * cos 20 + cos 20
2 * (-1/2) * cos 20 + cos 20
-cos 20 + cos 20
= 0.
Hope this helps!
78910:
but the answer is 1
any way you gave me an idea how to solve this problem thankyou
Okk Bro. You can report my answer. So that It gets deleted and someone else will answer.
answer is 1
Answered by
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ANSWER
.................
THIS IS THE QUESTION OF WHICH THE ANSWER IS GIVEN BY THE KVNMURTY
cos20+cos100=2cos(100+20)/2cos(100-20)/2
=2cos(60)cos(40)
=2*1/2*cos(40)
=cos(40)
cos20+cos100+cos140=cos40 + cos140
=2cos(40+140)/2cos(40-140)/2
=2cos90cos50
=2*0*cos50
=0
********************************************
THE CORRECT ANSWER IS 0 NOT 1
.................
THIS IS THE QUESTION OF WHICH THE ANSWER IS GIVEN BY THE KVNMURTY
cos20+cos100=2cos(100+20)/2cos(100-20)/2
=2cos(60)cos(40)
=2*1/2*cos(40)
=cos(40)
cos20+cos100+cos140=cos40 + cos140
=2cos(40+140)/2cos(40-140)/2
=2cos90cos50
=2*0*cos50
=0
********************************************
THE CORRECT ANSWER IS 0 NOT 1
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