Jawabanmu

2014-06-03T23:08:49+07:00
(cosec a + cot a - 1)(cosec a - cot a + 1)
cosec² a - cosec a.cot a  + cosec a + cosec a.cot a - cot² a + cot a - cosec a + cot a - 1

cosec² a - cot² a + 2 cot a - 1

(1 + cot² a) - cot² a + 2 cot a - 1

1 + cot² a - cot² a + 2 cot a - 1

2 cot a ........terbukti