Saturday

February 28, 2015

February 28, 2015

Posted by **Tara** on Monday, January 4, 2010 at 9:06pm.

Here's my book's explanation which I don't totally follow

sin x cos^2x-sinx=sinx(cos^2x-1)

=-sinx(1-cos^2x)

=-sinx(sin^2x) (Where does sine come from and what happend to cosine?)

=-sin^3x

- Trig -
**Reiny**, Monday, January 4, 2010 at 9:19pmsin x cos^2x-sinx=sinx(cos^2x-1)

**they took out a common factor of sinx**

=-sinx(1-cos^2x)**recall that sin^2x + cos^2x = 1, and then 1-cos^2x = sin^2x.**

Notice they had cos^2x-1 which is -(1-cos^2x). Also notice that there is now a - in front of the sinx

=-sinx(sin^2x) (Where does sine come from and what happend to cosine?)

=-sin^3x

**does it make sense now?**

**Answer this Question**

**Related Questions**

Math (trigonometric identities) - I was given 21 questions for homework and I ...

Mathematics - Trigonometric Identities - Prove: sin^2x - sin^4x = cos^2x - cos^...

Trigonometry. - ( tanx/1-cotx )+ (cotx/1-tanx)= (1+secxcscx) Good one! ...

Trig Help - Prove the following: [1+sinx]/[1+cscx]=tanx/secx =[1+sinx]/[1+1/sinx...

Mathematics - Trigonometric Identities - Reiny - Mathematics - Trigonometric ...

calculus - Could someone check my reasoning? thanx Find the derivative of the ...

Trigonometry - Prove the following trigonometric identities. please give a ...

Math - 1) evaluate without a calculator: a)sin(3.14/4) b) cos(-3(3.14)/4) c) ...

trig - I need to prove equality. a) (sina + cosa)^2 -1 / ctga - sinacosa = 2tg^...

Trigonometic - Solving Trigonometic Equations solve for x and give the answers ...