Question

Write the expression as either the sine, cosine, or tangent of a single angle.
cos(pi/3)cos(pi/5)+sin(pi/3)sin(pi/5)

Answer 1

this is the subtraction angle formula for cosine
i.e. it is
\[\cos(\frac{\pi}{3}-\frac{\pi}{5})\]

Answer 2

your job is to compute
\[\frac{\pi}{3}-\frac{\pi}{5}\]

Answer 3

satellite73 is using the identity

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

Answer 4

0.91354545764

Answer 5

zactly
btw don't be confused with the arithmetic
finding \[\frac{\pi}{3}-\frac{\pi}{5}\] is identical to
\[\frac{1}{3}-\frac{1}{5}\] then stick a \(\pi\) next to it

Answer 6

skip the decimals
work with a fraction

Answer 7

do you want a single fraction?

Answer 8

yes, a single fraction
although it is not really what I want, it is what the question wants
personally i don't care too much one way or the other
but in any case find \(\frac{1}{3}-\frac{1}{5}\)
put a \(\pi\) next to it
then write
\[\cos(\text{whatever})\]

Answer 9

let me know what you get and i will check it

Answer 10

2/15pi?

Answer 11

right so final answer is
\[\cos\left(\frac{2\pi}{15}\right)\]

Answer 12

Thank you so very much:)

Answer 13

yw