Wednesday

August 27, 2014

August 27, 2014

Posted by **Donovan** on Tuesday, January 6, 2009 at 6:46am.

Thanks

a)Express as a function of cos (theta)

2 sin^2(theta) - 1

b)Express as a function of sin (theta) or cos (theta)

tan^2(theta) - 2 sec(theta)sin(theta)

- Trig Identities -
**Reiny**, Tuesday, January 6, 2009 at 9:01amI will use x instead of theta for easier typing

2 sin^2 x - 1 = cos 2x

do you have to prove this?

if so, then

RS = -cos(2x)

= -cos(x+x)

= -cosxcosx + sinxsinx

= -cos^x + sin^x

= -(1-sin^x_ + sin^x

= 2sin^x - 1

= LS

- Trig Identities -
**Reiny**, Tuesday, January 6, 2009 at 9:05amfor the second

tan^x - 2secxsinx

= sin^2 x/cos^2 x - 2sinx/cosx

= sin^2 x/cos^2 x 2 sinxcosx/cos^2 x

= (sin^2 x - sin 2x)/(1 - sin^2 x)

this is in terms of sinx

**Related Questions**

Trig Identities - a)Express as a function of cos (theta) 2 sin^2(theta) - 1 b)...

Trig - How do you express these problems as single trigonometric function values...

Trig - How do you express these problems as single trigonometric function values...

Trigonometry - I don't understand how I'm supposed set the problem up or what ...

Trig - How do you express sin4x as a trigonometric funcition of x using the ...

trig - Work out the following identities a) sin theta/cos theta b) tan theta cos...

trig - in proving trigonometric identities if sec theta - tan theta sin theta is...

trig - what is the correct answer in proving trigonometric identities if tan ...

Trig - Column 1 Column 2 (sin theta + cos theta)sq 1 + 2sin theta cos theta ...

trig - in proving trigonometric identities if cot theta sin theta = cos theta. ...