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Jonask
 one year ago
Best ResponseYou've already chosen the best response.0\[\huge{\cos \frac{\pi}{7}}\cos \frac{2\pi}{7}+\cos \frac{3\pi}{7}=\frac{1}{2}\]

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0so far i managed to write \[\cos \frac{ \pi }{ 7 }2\cos^2\frac{ \pi }{ 7 }+1+\cos \frac{ 2\pi }{ 7 }\cos \frac{ \pi }{ 7 }\sin \frac{ 2\pi }{ 7 }\sin \frac{ \pi }{ 7 }\] \[\cos \frac{ \pi }{ 7 }2\cos ^2\frac{ \pi }{ 7 }+1+2\cos^3\frac{ \pi }{ 7 }\cos \frac{ \pi }{ 7 }2\cos \frac{ \pi }{ 7 }+2\cos^3\frac{ \pi }{ 7 }\] \[4\cos^3\frac{ \pi }{ 7 }2\cos^2\frac{ \pi }{ 7 }2\cos\frac{\pi}{7}+1\]

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0without using a calculator

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0guys i have the solution but it is so superficial i'll put it just now

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0is that the bookmark symbol

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2cos(pi/7) cos(2pi/7)+ cos(3pi/7) cos(pi/7)+cos(3pi/7)+cos(5pi/7) {2sin(pi/7)cos(pi/7) + 2 sin(pi/7) cos(3pi/7) + 2 sin(pi/7) cos(5pi/7)}/2 sin(pi/7)

shubhamsrg
 one year ago
Best ResponseYou've already chosen the best response.0That is just a comment, which will enable me to receive notifications whenever it gets discussed * is just a symbol, yes, bookmark symbol

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0are you saying cos 2 pi/7=cos 5 pi/7

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2cos(5pi/7) =cos(pi 2pi/7) = cos(2pi/7)

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2It is because cos(pia)=cosa

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2Now, u need to use 2 sinA cosB = sin(A+B)  sin(AB)

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2Sorry, The correct formula is 2 sinA cosB =sin(A+B) + sin(AB) =sin(A+B)  sin(BA)

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2=cos(pi/7) cos(2pi/7)+ cos(3pi/7) =cos(pi/7)+cos(3pi/7)+cos(5pi/7) ={2sin(pi/7)cos(pi/7) + 2 sin(pi/7) cos(3pi/7) + 2 sin(pi/7) cos(5pi/7)}/2 sin(pi/7) ={sin(2pi/7) sin(0) +sin(4pi/7) sin(2pi/7) +sin(6pi/7) sin(4pi/7)}/2sin(pi/7) ={sin(6pi/7)}/2sin(pi/7) ={sin(pi/7)}/2sin(pi/7) =1/2

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2sin(6pi/7) =sin(pi pi/7) =sin(pi/7)

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0okay that makes so much sense i guess elementary steps we skipped

Jonask
 one year ago
Best ResponseYou've already chosen the best response.0so we just had to play with\[\pi \pm \frac{\pi}{7}\]

sauravshakya
 one year ago
Best ResponseYou've already chosen the best response.2yep... and one formula
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