Friday

March 6, 2015

March 6, 2015

Posted by **Abbey** on Sunday, February 5, 2012 at 11:05pm.

- calculus -
**Reiny**, Monday, February 6, 2012 at 12:52amcos 2A = 2cos^2 A - 1

cos (π/6) = 2cos^2 (π/12) - 1

√3/2 + 1 = 2cos^2 (π/12)

cos π/12 = ±√(√3/4 + 1/2)

but /12 is in quadrant I

so cos (π/12) = √(√3/4 + 1/2)

or (1/2)√(√3 + 2)

**Answer this Question**

**Related Questions**

Pre-Calculus - I really need help on this question Simplify the expression by ...

pre-calc - simplfy the expression by double angle formula or a half angle ...

Trigonometry - I need to prove that the following is true. Thanks. csc^2(A/2)=...

math - Can anyone help w/ these. 1) Solve the equation in the internal [0deg, ...

Trigonometry - Identities - If tan 2x = - 24/7, where 90 degrees < x < 180...

math - Find the exact value of cos 300 degrees. thanks guys cos 300 = 1/2 = 0....

Trig/Precalc - So I have two questions that have been puzzling me for quite some...

pre-calc helpppp - Simplify the expression by using a Double-Angle Formula or a ...

Pre-Calc Help!!! - Simplify the expression by using a Double-Angle Formula or a ...

Algebra II - 1) Find the exact value of cos 105 degrees by using a half-angle ...