Question

how do i know

arccos -1/sqrt2 = 3pi/4

Answer 1

\[\theta=\cos^{-1} -1/\sqrt{2} \]

Answer 2

there is a unit circle you should memorize. i'll attach a pic in a sec

Answer 3

this is all stuff they will expect you to have memorized. well, the first and second quadrants atleast

Answer 4

since arccos is the inverse of cosine, you can rewrite the equation as: cos(3pi/4) =
-1/sqrt(2). And this is plainly true if you can quickly sketch the cosine function, which you should know.

Answer 5

hm, maybe i should learn it then.... would you just do that by wrote learning? isn't there a slightly easier way (takes slightly less time than wrote?)

Answer 6

the ordered pairs are (cos(theta),sin(theta))

Answer 7

Yes, you should memorize it, though there is a very nice reason why these functions look the way they do.. I would recommend the khan-academy.org website for an in depth explanation

Answer 8

i feel like i should know what an ordered pair is...

Answer 9

ordered pair: (x,y)

Answer 10

oh

Answer 11

gah, khan's voice annoys me.

Answer 12

lol

Answer 13

Paul Zord, what course are you taking?

Answer 14

You never learned unit circle?

Answer 15

its a first year subject

Answer 16

i've learnt it and forgotten it.

Answer 17

If you've learned it before, you can learn it again. It's easy....

Answer 18

paul:one of the great things aboput open study is that it allows you to revise all your basic concepts from ...a time long long ago

Answer 19

Unit circle is based on the fact that the radius of a circle is one and then you can find all of the other angles using triangles, special angles rules and trigonometry

Answer 20

And coverting between radians and degrees is easy because pi = 180

for example: 3pi/4 = 3(180)/4 = 3(45) = 135 degrees

Answer 21

radians = 135*(pi/180)