Question

is my work correct ?
here is the problem:
tan(arccos(-1/2)+arccos(2/3))
let A=arccos(-1/2)
let A=arccos(2/3)
tan(A+A)=tan(2A)
tan(2A)=2tanA/1-tan^2A
=2(-√3)/(1-(-√3)^2
=-2√3/1+3
=-2√3/4
=-√3/2

Answer 1

Hoot! You just asked your first question! Hang tight while I find people to answer it for you. You can thank people who give you good answers by clicking the 'Good Answer' button on the right!

Answer 2

you can't call two different things the same variable and then add them like they are the same.

Answer 3

there is an identity for tan(A+B) though

Answer 4

thats what i thought. but when i did it as tan(A+B) which would be tanA+tanb/1-tanAtanB it did not correspond with the answer my teacher gave which is -√3/3.

Answer 5

I think -sqrt(3)/3 is incorrect

Answer 6

what did you get?

Answer 7

-9√3+8√5/-13

Answer 8

maple is saying that isn't right. Let me work the problem.. one sec.

Answer 9

ok i got (-9sqrt(3)+8sqrt(5))/(-11)

Answer 10

thats what maple got too

Answer 11

ok so my numerator is right but my denominator is wrong. can you explain how you got the denominator?

Answer 12

my denominator was initially 1+sqrt(3)*sqrt(5)/2, so i multiplied top and bottom by the conjugate:
then in the denominator you get 1-15/4. In the numerator there was a common factor of 1/4 so i multiplied the denominator by 4:
4-15=-11

Answer 13

ohhh never mind i got it. thanks soo much for your help!!!

Answer 14

you're welcome :)

Answer 15

are you a musician?

Answer 16

yeah i play the cello&piano and i can carry a tune =) also how do i give you a medal for your answer?

Answer 17

oh if you want you click "good answer" in line with my name on one of my posts:

I play classical/jazz violin and guitar. I like cello and piano a lot.

Answer 18

ohh thats great ! nice to meet a fellow musician =)

Answer 19

well good luck with your math, talk to you later

Answer 20

thank you !

Answer 21

oh ok i got that.
could you have used the quadratic formula to solve the equation?