Idon't understand how to find the frequency and period of wavelengths. can anyone me?

What is the length x of the side of the triangle below? (hint: use the cosine function)

Laboratory experiments, observational field studies, and model-building are all examples of different forms of scientific investigations.  in what way do laboratory experiments primarily differ from other forms of scientific investigations?   a.  a laboratory experiment is the only accepted form of investigation within the scientific community.  b.  studies about how things behave in nature or studies involving very large objects are best answered through laboratory experiments.  c.  laboratory experiments involve the identification and control of variables.  d.  data can only be generated through laboratory experiments, not other forms of investigation.

In a system, when potential energy decreases, then entropy also decreases. true false