Two Transverse Sinusoidal waves combine in a medium

[Willjeezy]

Homework Statement

Two Transverse Sinusoidal waves combine in a medium are described by the wave functions:

y1 = 3sin∏(x + 0.600t)

y2 = 3sin∏(x - 0.600t)

what is y1 + y2?

Homework Equations

the hint is that I am supposed to use:
sin(α + β) = sin(α)cos(β) + cos(α)sin(β)

The Attempt at a Solution

the answer in the back is:
y = y1 + y2 = 6sin(∏x)cos(0.600∏t)

I am not really sure how they got that. In fact,the notation of y1 and y2 confuse me because y1 says:

y1=3sin∏(x + 0.600t)

and I interpret this as 3 multiplied by sin∏ multiplied by (x+0.600t)

but the problem is sin∏ = 0, so don't both equations just reduce to 0?

y1 = 0
y2 = 0?

Can someone clarify this for me?

 

[rude man]

y1=3sin∏(x + 0.600t)

and I interpret this as 3 multiplied by sin∏ multiplied by (x+0.600t)

No. 3sin[π(x + 0.6t)] means "three times the sine of the angle π(x + 0.6t)".

 

[Willjeezy]

hmm.3sin[π(x + 0.6t)]

it was written verbatim as:
3sin∏(x + 0.600t)

thanks, rude man.

 

[rude man]

hmm.

I wasn't sure if it was a typo, they are missing the outer square brackets

3sin[π(x + 0.6t)]

it was written verbatim as:
3sin∏(x + 0.600t)

thanks, rude man.

I just added the square brackets for emphasis for your benefit.

Why would anyone write "sinπ" when that quantity is zero?