P pl0oper New member Joined Sep 13, 2020 Messages 1 Sep 13, 2020 #1 I'm stuck. I need help. I need to see the whole process to know how to solve it. Thank You!

S Subhotosh Khan Super Moderator Staff member Joined Jun 18, 2007 Messages 22,083 Sep 13, 2020 #2 pl0oper said: View attachment 21588 I'm stuck. I need help. I need to see the whole process to know how to solve it. Thank You! Click to expand... Start with expanding cos(x+y), cos(x-y), sin(x+y) & sin(x-y) and simplifying the right-hand-side of the given identity. Please show us what you have tried and exactly where you are stuck.Please follow the rules of posting in this forum, as enunciated at:https://www.freemathhelp.com/forum/threads/read-before-posting.109846/#post-486520Please share your work/thoughts about this problem.

pl0oper said: View attachment 21588 I'm stuck. I need help. I need to see the whole process to know how to solve it. Thank You! Click to expand... Start with expanding cos(x+y), cos(x-y), sin(x+y) & sin(x-y) and simplifying the right-hand-side of the given identity. Please show us what you have tried and exactly where you are stuck.Please follow the rules of posting in this forum, as enunciated at:https://www.freemathhelp.com/forum/threads/read-before-posting.109846/#post-486520Please share your work/thoughts about this problem.

pka Elite Member Joined Jan 29, 2005 Messages 10,298 Sep 13, 2020 #3 \( \sin (x \pm y) = \sin (x)\cos (y) \pm \sin (y)\cos (x) \) \( \cos (x \pm y) = \cos (x)\cos (y) \mp \sin (x)\sin (y) \) SEE HERE I_______________SEE HERE II

\( \sin (x \pm y) = \sin (x)\cos (y) \pm \sin (y)\cos (x) \) \( \cos (x \pm y) = \cos (x)\cos (y) \mp \sin (x)\sin (y) \) SEE HERE I_______________SEE HERE II