Prove Tan^2 x +1= 1/cos2 x

Describe the 2 algebraic methods you can use to find the zeros of the function f(t)=-16t^2+400.

Aschool puts on a play. the play costs $1,200 in expenses. the students charge $4.00 for tickets. there will be one performance of the play in an auditorium that seats 500 people. what is the domain of the function that shows the profit as a function of the number of tickets sold?  

See attachment below and find the equivalent of tan(∠qsr)