✔ 最佳答案
Case 1
======
( sin θ / csc θ )+ cot θ
= sin^2 θ + ( cos θ / sin θ )
= ( sin^3 θ + cos θ ) / sin θ
= [ ( 1 - cos^2 θ )( sin θ ) + cos θ ] / sin θ
= [ ( - sin θ ) cos^2 θ + cos θ + ( sin θ ) ] / sin θ .......
Case 2:
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cscθ + cotθ
= 1/sinθ + cosθ/sinθ
= ( 1 + cosθ )/sinθ
sinθ/ [ ( cscθ + cotθ ) / sinθ ]
= sin^2 θ / ( 1 + cosθ )
= ( 1 - cos^2 θ ) / ( 1 + cosθ )
= ( 1 + cosθ )( 1 - cosθ ) / ( 1 + cosθ )
= 1 - cosθ
Both cases cannot reach your R.H.S answer.
Hence, it is not an identity.
Please check your question if there is any typing mistake or if it only askes you to check whether it is an identity.
Hope I can help you.
參考: Mathematics Teacher Mr. Ip