Assume Classical Ideas of Space and Time (Ether)

[knowLittle]

Homework Statement

My question is part C of problem 1.9:
http://facultyfiles.deanza.edu/gems/lunaeduardo/4DHW.PDF

Homework Equations

Pythagorean Theorem?

The Attempt at a Solution

I have c vector of lightwave going upwards and v going rightwards forming a right angle with the other vector.
Now, I need to find the observed speed of the lightwave on earth.
I would do √(c^2 + v^2), since the particles are being separated by the hypotenuse, but I think it's wrong I have seen some answers online that involve a minus sign for some reason.

Could someone elucidate?
Thank you.

 

[member 553083]

The answer to this question is the Pythagorean Theorem. The formula for the observed speed of the lightwave on Earth is c2 + v2, where c is the speed of light and v is the speed of the observer relative to the source. The minus sign is not needed because it is a vector equation, which means that the magnitude of the vectors is being calculated, not their direction.