Gunakan langkah dan cara

tan 25° = a

a][

tan (a + b) = (tan a + tan b) / (1 - tan a tan b)

tan 55° 
= tan (30° + 25°)
= (1/√3 + a) / (1 - a/√3)
= (1 + a√3) / (√3 - a)

(lampiran)

b][

tan 65° = cot 25° = 1/a

•••
(tan 205° - tan 115°)/(tan 245° - tan 335°)
= (tan 25° + tan 65°) / (tan 65° - (- tan 25°))
= (a + 1/a) / (1/a + a)
= 1

•••
sec (-127°)
= - sec (180° - 127°)
= - sec 53° 
= - 1/0,6
= -10/6
= - 5/3