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Question
Write the least value of cos2 x + sec2 x.
Solution
We know:
cos x can take the minimum value of -1.
cos2 x + sec2 x
\[= \frac{\cos^4 x + 1}{\cos^2 x}\]
\[ = \frac{\left( - 1 \right)^4 + 1}{\left( - 1 \right)^2}\]
\[ = 2\]
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