Elements with the same number of valence electrons have different properties have similar properties don't exist are located on opposite sides of the periodic table

In the 30-60-90 triangle below side s has a length of and side r has a length

What is the y intercept of f(x)=(1/2)^x?

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?