Friday

February 27, 2015

February 27, 2015

Posted by **Parker** on Friday, August 14, 2009 at 2:46pm.

- Math (Find the Value) -
**Marth**, Friday, August 14, 2009 at 4:09pmFirst solve cos(theta)=0.5

Step 1: Where is the cosine of theta equal to 0.5? Think about your memory angles or special triangles.

Step 2: Now double the angles found in step 1, and take the cosine of the new angle you found. (Both answers should be the same).

- Math (Find the Value) -
**MathMate**, Friday, August 14, 2009 at 9:01pmAnother approach using double angle identities.

cos(2A)=cos²(A)-sin²(A)=2cos²(A)-1

You will find cos(2A) by subtituting the value of cos(A) in the above equation.

**Answer this Question**

**Related Questions**

Pre Calc. - Use the sum or difference identity to find the exact value of sin255...

Pre-Calculus-check answers - If cos theta = 0.8 and 270<theta<360, find ...

math - There are no typos and no work b/c I don't know how to do them. Thanks. 1...

Math - sin theta = 8/17 and theta is in the second quadrant. Find sin(2theta),...

Calculus - I wanted to confirm that I solved these problems correctly (we had to...

Trig - 1. Establish the identity: sin(theta+3pi/2)=-cos(theta) 2. Find the exact...

Precalculus 2 - Similiarly to a question I asked previously I took the same ...

Algebra II - Which of the following expressions are not equal to 1? A) sin^2 ...

trig - given that 1/2pi<theta<pi and sin theta=1/5, use appropriate ...

Algebra II - Multiple Choice (theta) means the symbol 0 with the dash in it. 1.)...