Question

I give medalsssss
Write the expression as either the sine, cosine, or tangent of a single angle.
cosine of pi divided by five times cosine of pi divided by seven plus sine of pi divided by five times sine of pi divided by seven.

Answer 1

This is how far ive gotten
cos(pi/5-pi/7)+sin(pi/5-pi/7)
cos(7pi/35-5pi/35)+sin(7pi/35-5pi/35)
cos(2pi/35)+sin(2pi/35)

Answer 2

@thomaster

Answer 3

Is it:
\(cos\frac{\pi}{5}*cos\frac{\pi}{7}+sin\frac{\pi}{7}sin\frac{\pi}{5}\)
If the above expression is correct, then you can use the difference formula:
\(cos(x-y)=cos(x)cos(y)+sin(x)sin(y)\)

Answer 4

isnt that what i did?

Answer 5

I do not know what you solved because the problem you solved is different from what i posted. So please confirm what the problem is before we can figure out solutions.

Answer 6

cos(pi/5)cos(pi/7)+sin(pi/5)sin(pi/7)

Answer 7

ok, then the identity I suggested would help you.
You were close, but for a different reason.

Answer 8

i dont really understand what the question is asking...

Answer 9

The question wants you to recognize that the expression is either the sin, cos or tan function of a single angle, like cos(2pi/35), or sin(pi/24), etc.
If you examine the right-hand side of the identity I proposed, you will be able to convert the complicated expression into a single function of a single angle.

Answer 10

ok thanks!

Answer 11

You're welcome! :)