Question

if cos A =2÷5 find the value of 4 +4 tan 2A

Answer 1

i hope thats solving are right

Answer 2

Let the triangle be ABC right angled at B .

      AB=2
      AC=5
      BC=?

By pythagoras theorem ,

AC square = AB square +BC square
BC square = AC square - AB square
BC  square = 5 square - 2 square 
                   =  25 - 4
BC square  = 21
Thus BC = ROOT 21

tan A = root 21/2

4 + 4 (root 21/2 ) (root 21 / 2)
4+21
25

Hence the value is 25