I'm not sure the working step.

tan x + tan y = sin(x + y) / cos x + tan y

This my ans;

LHS = sin x cos y + cos x sin y / cos x cos y

= sin x + sin y

= tan x + tan y

= RHS

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- April 25th 2013, 07:02 PMchoi105Prove the following identities
I'm not sure the working step.

tan x + tan y = sin(x + y) / cos x + tan y

This my ans;

LHS = sin x cos y + cos x sin y / cos x cos y

= sin x + sin y

= tan x + tan y

= RHS - April 25th 2013, 07:57 PMchiroRe: Prove the following identities
Hey choi105.

I think you may have copied this down wrong.

Do you mean sin(x+y)/[cos(x) + tan(y)] instead? - April 25th 2013, 08:05 PMchoi105Re: Prove the following identities
yup.

- April 25th 2013, 11:29 PMibduttRe: Prove the following identities
The identity written is not true. Please recheck the question.

- April 26th 2013, 08:17 PMchoi105Re: Prove the following identities
sorry for typing error.

The que: tan x + tan y = sin(x + y) / cos x + cos y - April 26th 2013, 09:30 PMsa-ri-ga-maRe: Prove the following identities
Again it is wrong. Check the Dinominator.

- April 27th 2013, 12:06 AMibduttRe: Prove the following identities
I think RHS would be having cosx cos y in the denominator.

write tanx and tany in the form of sinx / cosx and siny/cosy. take LCM and use the formula for sum of angles the numerator and you have the result.