Question

prove that cos θ = 1/2 ( a + 1/a).

Answer 1

i didnt know it was possible to turn a variable into another without a conversion thingy...

Answer 2

is this only the question given?

Please check it again

Answer 3

What about "a"? What kind of variable?

Answer 4

yea .. it is the way it is given in my note .. but what do you think is right ?

Answer 5

@athe i dont know !

Answer 6

well i dont think that it is right :

Answer 7

Since we have a variable "a" in RHS ..

the main question arises that what kind of variable "a" is right ?

Answer 8

okay , then what do you think is the right question ?

Answer 9

there are many possible questions ..
hence i can not tell ..

Answer 10

i dont know .. i just started with my trig lessons !

Answer 11

https://www.google.co.in/search?q=prove+that+cos+%CE%B8+%3D+1%2F2+(+a+%2B+1%2Fa).&sugexp=chrome,mod=8&sourceid=chrome&ie=UTF-8

possible questions

Answer 12

:/

Answer 13

if

Answer 14

for example, if \[a=10 \] this equation senselessly.

Answer 15

a might be something like tan(theta/2)...some half angle trigo function...

Answer 16

i dont know .. i might very well close this question then !

Answer 17

multiply first.

Answer 18

thanks for the help anyway guys !

Answer 19

I think it is given

Answer 20

what is given ?

Answer 21

and maybe problem is to find \[a^2+\frac{1}{a^2}\] or something like this

Answer 22

@mukushla if the question is that how'd you do it ?

Answer 23

square both sides

Answer 24

by using 2cos^2 θ - 1 formula ?

Answer 25

idk what is the original problem...but if

\[a+\frac{1}{a}=2 \cos \theta\]then\[a^2+\frac{1}{a^2}+2=4 \cos^2 \theta\]

Answer 26

so 4cos θ = 2 cos^2 2θ - 1 ?

Answer 27

u dont need that formula

Answer 28

then how do you do it ?

Answer 29

its almost done....

Answer 30

tnx for the help !

Answer 31

np :)