Question

if cosA=2/5 find the value of 4+4tan2A

Answer 1

here,
         cosA =2/5

   now,we know that 
                               tan2A = (1-cos²A) / (1+cos²A)

       now 4+4tan2A =4 +4*{1-(2/5)²} / {1+(2/5)²}

        => 4+4{1- 4/25} / {1+4/25}
        => 4+4(25-4) / (25+4)
        => 4+84/29=(116 + 84) / 29 =200 /29 =6.89 answer
   
   hope it helps ........ 

Answer 2

hope this will help u