Question

What do I do if there is no pi/5 on the unit circle and I converted into degrees and it gave me 36, but there are no degrees when you add or subtract that give 36

Answer 1

What's the full problem?

Answer 2

to evaluate cos(pi/5) ? or something?

Answer 3

yea to make it a x and y @jim_thompson5910

Answer 4

Write the expression as either the sine, cosine, or tangent of a single angle.

cosine of pi divided by three times cosine of pi divided by five plus sine of pi divided by three times sine of pi divided by five.

Answer 5

oh i see, so this?

\[\Large
\cos\left(\frac{\pi}{3}\right)
*
\cos\left(\frac{\pi}{5}\right)
+
\sin\left(\frac{\pi}{3}\right)
*
\sin\left(\frac{\pi}{5}\right)
\]

Answer 6

yes that's it but the problem is wit the pi/5

Answer 7

you would use the identity

cos(x-y) = cos(x)*cos(y) + sin(x)*sin(y)

Answer 8

yea but i need to transform pi/5 into degrees and it's 36 degrees and it's not on the unit circle. I dont know how to do that

Answer 9

no you just use cos(x-y) = cos(x)*cos(y) + sin(x)*sin(y)

to convert the expression into a single trig function

Answer 10

your answer will be of the form cos(z)

where z is some number

Answer 11

ohhh so it would just be cos(pi/3 - pi/5)

Answer 12

you'd simplify that

Answer 13

simplify pi/3 - pi/5

Answer 14

okay let me try it

Answer 15

Cos(2pi/15) ?

Answer 16

perfect

Answer 17

I was over doing it thank you :D

Answer 18

you're welcome