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avatar+956 

If tanx = 6/8 what is cos2x that 0

 

Options: 

-8/5

8/5

-7/25

7/25 

 

I have 20 minutes so if you could be fast, I'd really really appreciate it :D

 Dec 13, 2017
 #1
avatar+99275 
+2

If tan x  =  6/8.....  this is a 6-8-10 right triangle......then cos x  =  8/10   ....so.....

 

cos 2x  = 2cos^2x  - 1

 

cos 2x  =  2(8/10)^2  -  1

 

cos2x =  2 (64/100)  -  1

 

cos2x  =  128/100  -  100/100 

 

cos 2x   =  28/100  =     7/25   

 

 

 

cool cool cool

 Dec 13, 2017

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