Bantu jawab yaa.........

i. Rumus identitas :
=> tan²x + 1 = sec² x
= 1 - cos²x = sin² x

tan² x = (1 + tan² x)(1 - cos² x)
tan² x = (sec² x)(sin² x)
tan² x = (1/cos² x)(sin² x)
tan² x = sin² x / cos² x
tan² x = tan² x ⇒ terbukti