Question

i need help with Write the expression as either the sine, cosine, or tangent of a single angle. cos pi/5 cos pi/7 + sin pi/5 sin pi/7

Answer 1

do you have a trig formulas sheet?

Answer 2

no

Answer 3

ok, check -> http://hyperphysics.phy-astr.gsu.edu/hbase/imgmth/trid1.gif
your answer is there

Answer 4

I'll brb

Answer 5

back :)

Answer 6

i still dont get it. :/

Answer 7

look at what you have, look at the sheet :), replace your angles for \[\alpha\ and \ \beta\] if you have to :)

Answer 8

is it like this