Question

prove :

2cos π/14+ cos9π/13+cos3 π/13/+cos5π/13=0

Answer 1

well your question is wrong

correct Question ▶

2cos π/13+ cos9π/13+cos3 π/13/+cos5π/13=0

For solution :

__see the attachment I think it will help you^_^

THANKS ❤:)

#Nishu HARYANVI ♠

Answer 2

Answer:

0

Step-by-step explanation:

Note: Your questions seems to be incorrect.

LHS:

Given : 2 cos(π/13) + cos(9π/13) + cos(3π/13) + cos(5π/13)

We know that cosa + cosb = 2 cos(a + b)/2 cos(a - b)/2

= 2 cos(π/13) + cos(9π/13) + 2 cos(8π/26) cos(-2π/26)

= 2 cos(π/13) + cos(9π/13) + 2 cos(4π/13) cos(-π/13)

= 2 cos(π/13) + cos(9π/13) + 2 cos(4π/13) cos(π/13)

= 2 cos(π/13)[cos(9π/13) + cos(4π/13)]

= 2 cos(π/13)[2 cos(13π/26) cos(5π/26)]

= 2 cos(π/13)[2 cos(π/2) cos(5π/26)]

= 2 cos(π/13)[0]

= 0.

= RHS

Hope it helps!