establish the identity

[r8654]

Hello again. Since i was kindly helped by so many people for my last question i thought i could ask another. I need to establish the identity.
sec(x+y)=

Sec(x)Sec(y)
___________
1-tan(x)Tan(y)

Thanks

 

[Loren]

I think it will be easiest to start on the right side and work toward the left side.
Put the right side into terms of sin and cos. In the numerator you should get 1/(cos x cos y) and in the denominator you should get 1 - (sin x)/(cos x)·(sin y)/(cos y). Now, combine these into one fraction. Now you have a complex fraction (a fraction in the numerator and a fraction in the denominator). Multiply both numerator and denominator by the reciprocal of the denominator. After simplifying this result you should get 1/(cos x cos y - sin x sin y). You can go from there???

 

[r8654]

yes. i think i got it. Thank you