Product tan a tan b tan 45 tan(90-b) tan(90-a): value 1

The same question, asked 2 times: 21 Jul 2023 S2*, 24 Jul 2023 S2. Every wording below, oldest first.

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Question 1
21 Jul 2023 S2
73 $\tan 25^\circ \tan 35^\circ \tan 45^\circ \tan 55^\circ \tan 65^\circ$
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Question 2
24 Jul 2023 S2
72 $\tan 5^\circ \tan 25^\circ \tan 45^\circ \tan 65^\circ \tan 85^\circ$
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