Answer:
Explanation:
note :
tanx = sinx/cosx and secx = 1/cosx
1+tan²(2π/3) = 1+(sin2π/3/cos2π/3)²
= 1 +( sin2π/3)²/(cos2π/3)²
=( sin2π/3)²+(cos2π/3)²/(cos2π/3)²
but : ( sin2π/3)²+(cos2π/3)²=1
so :1+tan²(2π/3) = 1 /(cos2π/3)²
=( 1/cos2π/3)²
:1+tan²(2π/3) =sec²( 2π/3)