if cos A= 2/5, then find the value of 4 + 4tan2 A
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Given that cos A=2/5
Now 4+4tan^2A = 4+4 tan x tan A
Since cos A = 2/5, therefore sec A = 1/ cos A= 5/2
So 4+ 4 tan^2A = 4(1+tan^2A)=4(5/2)(5/2)=4(25/4)=25
Hence 4+4 tan^2A= 25
Now 4+4tan^2A = 4+4 tan x tan A
Since cos A = 2/5, therefore sec A = 1/ cos A= 5/2
So 4+ 4 tan^2A = 4(1+tan^2A)=4(5/2)(5/2)=4(25/4)=25
Hence 4+4 tan^2A= 25
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