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Butterfly16
 3 years ago
Find an exact value.
cos 15°
Options:
A) sqrt 6 + sqrt 2 / 4
B)  sqrt2 + sqrt 6 / 4
C)  sqrt2  sqrt 6 / 4
D)  sqrt6 + 1 / 4
Butterfly16
 3 years ago
Find an exact value. cos 15° Options: A) sqrt 6 + sqrt 2 / 4 B)  sqrt2 + sqrt 6 / 4 C)  sqrt2  sqrt 6 / 4 D)  sqrt6 + 1 / 4

This Question is Closed

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0A) \[ \frac{ \sqrt{6}+\sqrt{2} }{ 4 } \] B) \[\frac{ \sqrt{2} +\sqrt{6} }{ 4 }\] C) \[\frac{ \sqrt{2}  \sqrt{6} }{ 4 }\] D) \[\frac{ \sqrt{6} +1}{ 4 }\]

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2cos(ab)=cosa cosb + sina sin b you know? if ok cos (4530)= cos45 cos 30 +sin 45 sin 30

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0where did you get all the numebrs?

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2dw:1357845575004:dw I dont get what you mean !

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0But its for cos 15° ?

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2It is an unknown angle you have to make it bu known angle

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2you know that formula? if yeah put the numbers in it you will have answer (a)

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0I think I got it. Can you help with another?

klimenkov
 3 years ago
Best ResponseYou've already chosen the best response.0Also, you can use \(\cos^2\frac x 2=\frac{1+\cos x}2\).

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0@klimenkov Can you help with this one, pelase? Write the expression as either the sine, cosine, or tangent of a single angle. \[\cos(\frac{ \pi }{ 5 }) \cos(\frac{ \pi }{ 7 }) + \sin (\frac{ \pi }{ 5}) \sin (\frac{ \pi }{ 7 })\]

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2as "klimenkov " says you can use that formula shuch the way i drawdw:1357846727839:dw

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2cos(π/5)cos(π/7)+sin(π/5)sin(π/7)=cos (π/5π/7) by the formula AS i sayd before cos (a+b)= cos a cos bsin a sin b

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0so would the cos (a+b) be pi/5+pi/7?

klimenkov
 3 years ago
Best ResponseYou've already chosen the best response.0No. It will be \(\cos(\frac\pi5\frac\pi7)\) as @amoodarya said. Hope you can do this subtraction.

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2no i think that you get it cos (a+b)= cos a cos bsin a sin b cos (ab)= cos a cos b+sin a sin b but 2pi/35 is unknown angle

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0\[\cos(\frac{ \pi }{ 5 }+\frac{ \pi }{ 7 })\] is 2pi/35? Can you show me how to fill in the formula? I think it'd make it easier for me.

amoodarya
 3 years ago
Best ResponseYou've already chosen the best response.2cos (ab)= cos a cos b+sin a sin b a=pi/5 b=pi/7

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0cos (pi/5pi/7)= cos (pi/5) cos (pi/7)+sin (pi/5) sin (pi/7) ?

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0So the answers 2pi/35?

klimenkov
 3 years ago
Best ResponseYou've already chosen the best response.0No. The answer is \(\cos(\frac{2\pi}{35})\).

Butterfly16
 3 years ago
Best ResponseYou've already chosen the best response.0That's what I said?

klimenkov
 3 years ago
Best ResponseYou've already chosen the best response.0You said this without cosine.
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