Question

TRIG EXPANSIONS!!
http://gyazo.com/ba80a4ed15d361318e9c594f2ced1cb5

Answer 1

\(\cos(A+B)=\cos A\cos B-\sin A\sin B\)
\(\sin2A=2\sin A\cos A\)
\(\sin^2A+\cos^2A=1\)
\(\sin^2A=1-\cos^2A\)
Does that help? @kausarsalley

Answer 2

\[\Large cos(3x) = cos(2x)cos(x) - sin(2x)sin(x) \]
\[\Large [2cos^{2}(x) - 1]cos(x) - 2sin(x)cos(x)sin(x) \]
\[\Large 2cos^3(x) - cos(x) - 2sin^{2}(x)cos(x) \]
\[\Large 2cos^3(x) - cos(x) - 2cos(x)(1 - cos^2(x) \]
\[\Large 2cos^3(x) - cos(x) - 2cos(x) + 2cos^3(x) = 4cos^3(x) - 3cos(x) \]

Answer 3

Don't Forget that :
\[\Huge \color{Red}{sin^2(x) + cos^2(x) = 1}\]

Answer 4

I am trying to solve it again using the identities you have given me ......thank you :)

Answer 5

ha k. welcome:)