Thursday

October 23, 2014

October 23, 2014

Posted by **trista** on Tuesday, February 24, 2009 at 6:48pm.

pie/8

and

pie/12

- precal -
**bobpursley**, Tuesday, February 24, 2009 at 6:55pmI will be happy to check your thinking on this.

- precal -
**trista**, Tuesday, February 24, 2009 at 7:02pmi honestly dont know what to do or how to start anyways

- precal -
**Reiny**, Tuesday, February 24, 2009 at 8:37pmthe half-angle formulas let you split an angle in half

there is sin 2A = 2sinAcosA and

cos 2A = cos^2 A - sin^2 A or

cos 2A = 2cos^2 A - 1 or

cos 2A = 1 - 2sin^2 A

I will do the pi/12 angle for you.

pi/6 rads = 30 degrees, and pi/12 = 15 degrees

From the 30-60-90 triangle you should know

sin30 = 1/2 and cos30 = ?3/2

cos 30 = 1 - 2sin^2 15

2sin^2 15 = 1-?3/2

sin ^2 15 = 1/2 - ?3/4

= (2-?3)4

so sin 15 = ?(2-?3)/2

or sin pi/12 = ?(2-?3)/2

now ;use the other version of cos 2A to get cos pi/12

and since tanx = sinx/cosx, divide the two results to get the tangent.

verify your answer with your calculator

for the first pi/8 is half of pi/4 which is 45 degrees

you should know the trig rations for 45 degrees.

**Answer this Question**

**Related Questions**

maths - Choose the two options which are true for all values of x 1) cos (x) = ...

MATH - 1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL ...

Pre calc - Use the half-angle formulas to determine the exact values of the sine...

physics - The motion of a particle is described by x = 10 sin (piet +pie/2 ). At...

Trig - Use the half angle formula to find the exact value of tan 7 pie/8

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

calculus - Hi i have two questions: what is the exact value of cos 5(pie)/12? ...

math - um take home test...i have no idea what im doing always sometimes never 1...

Calculus grade 12 - solve for (<_ = less than or equal to / pie = pie sign...

math - evaluate the expressions below and leave them in radical form. 1. sin(pie...