Question

Find the exact value of sin 82.5

Answer 1

you can write it as cos 7.5
then use half angle formula which is 1+cos 2x=2cos^2 x , use it two times firstly x=15 deg
then x=7.5 degrees

Answer 2

I know what forumla to use I am just stuck on if I have to find the cos of 165

Answer 3

I thought you had to muiltply it

Answer 4

165?? i dont think you have to go that much far :P

Answer 5

I'm so confused, oi

Answer 6

still after that explanation?

Answer 7

Ok... so.. you subtract 90-32.5=7.5

Answer 8

82.3*

Answer 9

Then you do \[\sqrt{1-\cos(2)(7.5)}\]

Answer 10

all over two right?

Answer 11

actually firstly you have to find 15 degrees by this formula coz we know the value of cos 2(15) then after use that formula again for 7.5

Answer 12

so it will be \[\sqrt{1-\cos15}\]

Answer 13

so you dint got what i said!!??

Answer 14

no i don't because i don't get how you get 15 then divide again when you have to use to formula to muiltiply it.

Answer 15

then divide my two

Answer 16

i'll get 15 by {(1-cos 30 )^1/2}/2

Answer 17

omg... where are you getting 30 now ??

Answer 18

you dont the value of cos 30?

Answer 19

..... I know the cos of 30 smart one I'm asking how you got it because from 90-82.5= 7.582=15

Answer 20

wait for 5 mnts i'll upload a SS

Answer 21

ok

Answer 22

so are you confused how i wrote sin 82.5 = cos 7.5... right?

Answer 23

yes

Answer 24

http://en.wikipedia.org/wiki/Unit_circle

Answer 25

tell if u get something from this

Answer 26

Ok listen I don't have all day to read this. I am just donfused on how to start the problem.

Answer 27

I don't want to sound feathery or anything but I need acutal help

Answer 28

ok... i get it :D

Answer 29

then getting to the point Transformation rules are:-
sin 90-x = cos x, same as tanx and cot 90-x

Answer 30

and sec and cosec also

Answer 31

sin x= 1/cosec x, cos x=1/ secx, tan x=1/cotx

Answer 32

well what do you say? :D

Answer 33

Not helpful. I';m sorry. It doesn't help me. I need to know how to to set up the problem.