I need show the following is an identity. (thanks)

cos(3t)=4cos^3(t)-3cos(t)

Printable View

- July 19th 2013, 07:42 PMTrimHondurasPlease help me on my Homework.
I need show the following is an identity. (thanks)

cos(3t)=4cos^3(t)-3cos(t) - July 19th 2013, 08:04 PMchiroRe: Please help me on my Homework.
Hey TrimHonduras.

Hint: Try using the sum of angles of formula to get cos(3t) down to cos(2t), cos(t), sin(2t) and sin(t) and then use it again to get sin(2t) in terms of sin(t) and cos(t) and also cos(2t) in terms of sin(t) and cos(t) and then collect everything together. - July 19th 2013, 08:25 PMTrimHondurasRe: Please help me on my Homework.
- July 19th 2013, 08:25 PMTrimHondurasRe: Please help me on my Homework.
So far I got that but I don't know what to do next.... maybe I got something wrong...