How to show these kind of equations? (1 Viewer)

[hit patel]

Show that tan3x=4cos^3(x)+3cosx when x=225 degrees.

I tried this but still cant show this.
Please help and also please show how to do other problems this way.

Thanks

 

[Kurosaki]

Show that tan3x=4cos^3(x)+3cosx when x=225 degrees.

I tried this but still cant show this.
Please help and also please show how to do other problems this way.

Thanks

Dont u just sub it in? Lol. I tried compound angle but got nowhere :/
plus it gives a specific value for which you need to show, so I think you just need to sub it in, and show LHS=RHS. how many marks was this Q worth?

 

[hit patel]

Dont u just sub it in? Lol. I tried compound angle but got nowhere :/
plus it gives a specific value for which you need to show, so I think you just need to sub it in, and show LHS=RHS. how many marks was this Q worth?

I tried subbing it in but i got different answer. how would you do tan3x would you do tan(3 times 225) and how many answers would u get i only got 1 and still cant show that LHS=RHS.

Thanks

 

[Kurosaki]

maybe you copied it down wrong?
I tried compounding using tan(2x +x)
On the LHS

 

[cineti970128]

the question is wrong

 

[Kurosaki]

the question is wrong

Yes, I was right! :-D (lol)

 

[hit patel]

the question is wrong

Ok thanks kurosaki and cineti. BTW cineti, i am aiming for similar results but suspect otherwise.

 

[AnimeX]

hm, should be cos3x not tan

 

[hit patel]

oh thanks animex.