Find the length of right side of a triangle if a=2,b=4 so c=?

c = sqroot ( a ^ 2 + b ^ 2 )

c = sqroot ( 2 ^ 2 + 4 ^ 2 )

c = sqroot ( 4 + 16 )

c = sqroot ( 20 )

c = sqroot ( 4 * 5 )

Remark: sqroot ( 4 ) = 2

c = 2 sqroot ( 5 )