Sketch the graph f(x)=sin(x)-cos(x)

Answer 1

there are lots of online graphing sites. However, this could help.
sinx - cosx
= √2 (sinx * 1/√2 - cosx * 1/√2)
= √2 sin(x - π/4)

Answer 2

confirming oobleck
https://www.wolframalpha.com/input/?i=plot+y+%3D+sinx+-+cosx%2C+y+%3D+%E2%88%9A2+sin%28x+-+%CF%80%2F4%29

Math is such fun when in self-quarantine.