Question

Rewrite sqrt(1+cos 45/2 using a half-angle identity.

sin 22.5°
cos 22.5°
sin 90°
cos 90°

Answer 1

since this time you have to use those formulas, we can't use arctan this time :P

Answer 2

ok

Answer 3

tan^(-1)(x)?

Answer 4

I hate this sht

Answer 5

no, you have to take the right side of the half angle formula and basically come up with the angle

Answer 6

\[\cos \frac{ a }{ 2 } = \sqrt{\frac{ 1+\cos(a) }{ 2}}\]

Answer 7

where a is the angle

Answer 8

\[\sin \frac{ a }{ 2 } = \sqrt{\frac{ 1-\cos(a) }{ 2 }}\]

Answer 9

It gives you the angle, so which one is it given the formula?

Answer 10

trying to plug them in my calculator

Answer 11

ins't it sin 22.5?

Answer 12

If it was sin, would there be a + or - in the formula?

Answer 13

so its cos 22.5

Answer 14

Yes

Answer 15

this is a better website, http://www.trans4mind.com/personal_development/mathematics/trigonometry/HalfAngles.htm

Answer 16

The first one I posted had too many things going on for even me to want to look at

Answer 17

Which expression is equivalent to cos(4x) + cos(2x)?

Answer 18

2cos(3x)cos x
-2sin(3x)sin x
2sin(3x)sin x
-2cos(3x)cos x

Answer 19

Do you know the double angle formula?

Answer 20

yea it does have to many formulas gives me head ache just looking at it

Answer 21

4x is just a double double angle :P

Answer 22

you want me too open a new question and post it their so you will get your medals?

Answer 23

I don't really care. Do it because I actually have to do something really fast

Answer 24

ok

Answer 25

so someone else will answer when I'm gone