If 90 degree < x < 180 degree, which of the following must be positive?(adsbygoogle = window.adsbygoogle || []).push({});

A.sinx+tanx

B.cosx+tanx

C.sinx+cosx

D.sinx-cosx

I don't know how to do this question, what method can I use?

Thanks.

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# Homework Help: Maths about trigo.

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