alleryChoose the correct value of $9\sec^2 A-9\tan^2 A$.
A1
B9
C8
D$\theta$
Answer & Solution
Correct answer: B. 9
Use the identity $\sec^2 A-\tan^2 A=1$.
Multiplying both sides by 9 gives $9\sec^2 A-9\tan^2 A=9$.
**Option A is a common mistake from forgetting the factor 9.**
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