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Grade: 11 

                        
prove that the following is true- cos 2 A+cos 2 B+cos 2 C=1-2cosAcosBcosC
4 years ago

Answers : (1)

Vikas TU
12157 Points 
							
Take R.H.S,


1-2cosAcosBcosC,


apply 2cosAcosB formulae and split into a+b form .


Then write 1 as (sinA)^2 + (cosA)^2 and the sort out u would get L.H.S
4 years ago
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