Sunday

March 1, 2015

March 1, 2015

Posted by **Brian** on Monday, April 20, 2009 at 1:56pm.

Rewrite the expression as an equivalent expression that does not contain powers greater than 1.

Cos³x

My answer: cos³x=(cos²x)(cosx)

=(1+cos2x/2)(cosx)-->cos+cos³x/2...which is wrong

- trig--power reducing formulas -
**Count Iblis**, Monday, April 20, 2009 at 4:04pmYou have to use doubling formulas again to express it in terms of cos(3x). If you know about complex numbers then the derivation is easy:

cos(x) = [exp(i x) + exp(-i x)]/2

cos^3(x) = 1/8 [exp(3 i x) +

exp(-3 i x)+ 3 exp(ix) + 3 exp(-ix) ] =

1/4 cos(3 x) + 3/4 cos(x)

- trig--power reducing formulas -
**sierra**, Sunday, November 18, 2012 at 7:00pm(cosx)+(cosx)(cosx)

**Answer this Question**

**Related Questions**

pre-cal - Simplify the given expression........? (2sin2x)(cos6x) sin 2x and cos ...

Trig - prove the identity (sinX)^6 +(cosX)^6= 1 - 3(sinX)^2 (cosX)^2 sinX^6= ...

Math - Can someone please check my answers! 2. Find value of cos(255degrees)cos(...

Math - 1. use the suitable product-to-sum formula to rewrite the following ...

Mathmatics - a. Use the formulas for lowering powers to rewrite the expression ...

Please help Math - a. Use the formulas for lowering powers to rewrite the ...

Calc II - For the following question, we need to find the length of the polar ...

Math - Explain how to do this with steps please. 1. Simplify cos(x-y)+cos(x+y)/...

Math - Explain how to do this with steps please. 1. Simplify cos(x-y)+cos(x+y)/...

pre-calc - Solve: cos(2x-180) - sin(x-90)=0 my work: cos2xcos180 + sin2xsin180= ...