Tuesday

September 23, 2014

September 23, 2014

Posted by **Anonymous** on Saturday, November 24, 2007 at 7:07pm.

Equation:

sin2x = 2cos2x

Answers:

90 and 270

....

My Work:

2sin(x)cos(x) = 2cos(2x)

sin(x) cos(x) = cos(2x)

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

cos(x) (+/-)\sqrt{1 - cos^2(x)} = 2cos^2(x) - 1

cos^2(x)(1 - cos^2(x)) = 4cos^4(x) - 4cos^2(x) + 1

5cos^4(x) - 5cos^2(x) + 1 = 0

cos(x) = (+/-) 0.85065080835215

cos(x) = (+/-)0.52573111211905

- Math - Solving Trig Equations -
**bobpursley**, Saturday, November 24, 2007 at 7:33pmwouldn't it be easier to solve for 2x then divide it by two?

sin2x=2cos2x

sin2x/cos2x=2

tan 2x=2

2x=63.43 deg

x= .... you do it.

**Answer this Question**

**Related Questions**

Math - Solving for Trig Equations - Solve the following equation for 0 less than...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

tigonometry - expres the following as sums and differences of sines or cosines ...

Precal - I do not understand how to do this problem ((sin^3 A + cos^3 A)/(sin A...

trigonometry (please double check this) - Solve the following trig equations. ...

Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...

Math - Solving Trig Equations - Solve each equation for o is less than and/or ...

trig - Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...

Math - Calculus - The identity below is significant because it relates 3 ...

Math, derivatives - f(x) = x² + 2Cos²x, find f ' (x) a) 2(x+cos x) b) x - sin x ...