Question

Buktikan tan^2 A - 1 / sec^2 A = tan^2 A - 1

Answer 1

Tan^4 a -1/sec²a = tan²a-1
tan^4 a -1/1+tan²a = tan²a-1
tan^4 a -1 = (tan²a + 1)(tan²a - 1)
tan^4 a -1 = tan^4 a-1

Answer 2

Ingat bahwa :
sec² A = tan² A + 1

maka :
tan⁴ A - 1/sec² A = tan² A - 1
((tan² A - 1)(tan² A + 1)) / (tan² A + 1) = tan² A + 1
tan² A - 1 = tan² A - 1  ⇒  Terbukti