You must understand the concept behind the equal sign. You're right in the fact that 1/cos^2(x) = sec^2(x) because that's just squaring both sides of 1/cos(x) = sec(x). Remember that whatever you do to one side of the equation, you must do to the other.
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You must understand the concept behind the equal sign. You're right in the fact that 1/cos^2(x) = sec^2(x) because that's just squaring both sides of 1/cos(x) = sec(x). Remember that whatever you do to one side of the equation, you must do to the other.