- Choice E
It should be remembered that:
sin2 A + cos2 A = 1
⇒ cos A = ± 12/13
As can be seen from the diagram, in the domain from 0 to 2π (0°-360°), it is possible for cos A to be negative.
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It should be remembered that:
sin2 A + cos2 A = 1
⇒ cos A = ± 12/13
As can be seen from the diagram, in the domain from 0 to 2π (0°-360°), it is possible for cos A to be negative.
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