tan(-225°)cot(315°)+tan(765°)cot(675°)=0
Prove that?
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this implies
-tan(90×2+45)×cot(90×3+45)+tan(90×8+45)×cot(90×7+45)
=-(-tan 45)×(-tan 45)+tan 45×tan45
= 1×-1 + 1×1
=-1+1=0
-tan(90×2+45)×cot(90×3+45)+tan(90×8+45)×cot(90×7+45)
=-(-tan 45)×(-tan 45)+tan 45×tan45
= 1×-1 + 1×1
=-1+1=0
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