Question

tan225 + tan 345÷ tan 195 - tan 105​

Answer 1

Answer. Put cot15=m

(tan 255 + tan 345)/(tan 195 - tan 105)

= {tan (270 - 15) + tan (360 - 15)}/{tan (180+15) - tan (90+15)}

= (cot 15 - tan 15)/(tan 15 + cot 15)

= (m - 1/cot15)/(1/cot15 + m)

= (m - 1/m)/(1/m + m)

= (m^2 - 1) / (m^2 + 1)