1.

2) Prove the following:cos ( 7 + x) cos(-x)= cotx

Answer»

-cos x^2/sinx.-sinxcosx^2/sinx^2=cotx^2

numerater:cos(π+x)=-cos x.•. it lies in 3rd quadrant,where cosine is -ve. &, cos(-x) =-cos xSo,numerater:(-cos x)(-cos x)



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