Question

Prove the cofunction identity using the addition and subtraction formulas. tan(pi/2 -u)= cot u

Answer 1

use the identities they asked you to use what's stopping you?
tan(a-b)=sin(a-b)/cos(a-b)
sin(a-b)=sinacosb-sinbcosa
cos(a-b)=cosacosb+sinasinb
go now and work on it

Answer 2

According to my teacher, I have to use the formula tana+tanb/1-tanatanb

Answer 3

\[\tan(a+b)=\frac{\tan(a)+\tan(b)}{1-\tan(a)\tan(b)}\]
then replace a with pi/2 and replace b with -u

Answer 4

I did that

Answer 5

ok and what did you get?

Answer 6

the only problem is tan(pi/2) is not going to work out

Answer 7

so i don't know why the teacher suggested that

Answer 8

or said you had to use it

Answer 9

I can't seem to break it down

Answer 10

i'm saying you can't use that identity your teacher provided because it doesn't work

Answer 11

tan(pi/2) doesn't exist

Answer 12

what i would do is draw a pretty little triangle

Answer 13

and assign variables to each of the sides of that triangle (being a right triangle)

Answer 14

then I would bind tan(pi/2-u) and cot(u)

Answer 15

and see if they were the same ratio