PLEASE HELP

A pendulum is swinging back and forth. After t seconds, the horizontal distance from the bob to the place where it was released is given by H(t)=7−7cos( 2π(t−2)/20). How often does the bob cross its midline? Give an exact answer.

Atemperature of 1.64◦f corresponds to answer in units of ◦c.

What are the excluded values? m+5/mn+3m

Sara goes on a slingshot ride in an amusement park. she is strapped into a spherical ball that has a radius 3*10^2 of centimeters. what is the volume of air in the spherical ball? use this formula: volume of a sphere=4/3pi, r^3 , where r is the sphere’s radius.