Can You Prove This Trig Identity? | A Level Maths

[@peace2863]

4 lines is all it took, LHS=2 cos2X.cosX + 2 cos4XcosX =2cosX(cos2X+cos4X) =2cosX(2cos3XcosX) =4cos3Xcos^2 X =RHS

[@jillian9098]

Can you explain how you got ur first line of working pls

[@peace2863]

​@@jillian9098 So basically what I did was just took 2cos 3X separately, so you get cosX + cos3X + cos3X + cos5X. The reason for that was I saw it had cosX in the answer , when we apply the addition rule we get a common 2cos X which we can take out

[@Pramittt]

15 mins for a question is crazy

[@NeilDoesMaths]

You guys have it easy rn

[@KushagraSaxena-j3p]

I got another solution Cosx + cos5x+ 2cos3x =2cos((5x+x)/2)cos((5x-x)/2)+ 2cos3x =2cos 3x cos2x+ 2cos3x =2cos3x(cos2x+1) =2cos3x((2(cosx)^2)-1+1) =4cosx^2.cos3x

[@NeilDoesMaths]

This is far quicker but unfortunately not in the A-Level specification anymore

[@KushagraSaxena-j3p]

But sir as we already got the solution,and there's no mistake in this so what's the need to worry about specifications?

[@asterecho2119]

FYI take cosx +xos3x +cos3x+cos5x and solve it’ll be much easier

[@Pramittt]

clipped 7:24

[@NeilDoesMaths]

Oh hell nahhhhh 😂😂😂😂

[@kealebogagalempoloke]

Sir can you please do tutorial on the whole topic of trig identies

[@NeilDoesMaths]

Yep I'll be releasing over time

[@kealebogagalempoloke]

@NeilDoesMaths thank you sir coz l do add maths and its giving me quite a challenge

[@SaarthShah-11]

I have a shorter soln, cud any1 guide me how to contact Mr.Neil?

[@MuzammilMirza-cl8ys]

Me also

[@oscarandresdiazgonzalez6982]

Thank you bro, follow doing this bro, follow your dream

[@NeilDoesMaths]

Noicéêë

[@gayathrikumar5643]

Wow that was tricky

[@NeilDoesMaths]

Trust me. My brain was deteriorating

[@peace2863]

Wait

[@BarcaEditz.]

As a year 9, I am confusion 💀

[@MholiMkhize-t6w]

You'll get it on day

[@NeilDoesMaths]

Next lesson I'll do it with you guys

[@BarcaEditz.]

@@NeilDoesMaths yay

[@AlaraDoesArt]

Sir you lied 😢

[@BarcaEditz.]

@ fr

[@toobin4life]

Lost!

[@HasanMUTD]

Gramp cooking too much 🤕

[@NeilDoesMaths]

Man like Hasan