1.

9 sec2A − 9 tan2A is equal to A. 1 B. 9 C. 8 D. 0

Answer»

To find: 9 sec2A – 9 tan2

Consider 9 sec2A – 9 tan2A = 9 (sec2A – tan2A) 

∵ 1 + tan2A = sec2

∴ 9 sec2A – 9 tan2A = 9 (sec2A – tan2A) 

= 9 (1 + tan2A – tan2A) = 9



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