tan 105 derajat cot 15 derajat

Trigonometri

tan 105. cot 15 = (sin 105 . cos 15)/(cos 105.sin 15)
= 1/2 ( 2 sin 105 .cos 15)/ 1/2 (2 cos 105 sin 15)
= (sin 120 + sin 90) / (sin120 - sin 90)
= (1/2 √3+ 1)/ (1/2 √3 - 1)
= (1/2 √3 +1)(1/2 √3 +1) / (1/2 √3 -1)(1/2 √3 +1)
= (3/4 + 1 + √3) / (3/4 -1)
= (3/4 + 1 + √3)/ (-1/4)
= -4 (3/4  + 1 + √3)
= -3 - 4 - 4√3
= -7 -  4√3
= -(7 + 4√3)