What is x if sin²x=cos²x?

My answer key says 0 is one of the answers and I'm not so sure about that. Can anyone explain why 0 would be one of the answers?

Alonso walked with his friend andy one day, and wanted to compare their speeds. alonso walked 3 miles in one hour, and andy walked 2 miles in 2 hours. complete the table to graph the relationship for each person.

Adj has a total of 1075 dance and rock songs on her system. the dance selection is 4 times the size of the rock selection. write a system of equations to represent the situation.

If a 36 inch yardstick casts a 21 foot shadow, how tall is a building whose shadow is 168 feet? what is the scale factor