Solving simple trig equation

Question

I tried to solve a simple trig equation.

Solve[{Sin[x] == Cos[x], 0 <= x <= Pi}];

The answer should be pi/4

But I get

simplify[{{x -> -2 ArcTan[1 - Sqrt[2]]}}]

Use FullSimplify[-2 ArcTan[1 - Sqrt[2]]] to give Pi/4. – flinty Jul 07 '20 at 01:52 — flinty, Jul 07 '20 at 01:52
This is the answer. thanks!! – smellerbee Jul 07 '20 at 01:55 — smellerbee, Jul 07 '20 at 01:55

score 0 · Answer 1 · answered Jul 07 '20 at 01:58

0

Try

FindRoot[Sin[x] - Cos[x], {x, 0}]

answered Jul 07 '20 at 01:58

PaulCommentary

`FindRoot[Sin[x] - Cos[x], {x, 0}] /.
r_Real :> Pi*RootApproximant[r/Pi]`
– Bob Hanlon Jul 07 '20 at 05:17
this doesn't give the value pi/4, but an numerical approximation though. Full Simplify has worked for me. – smellerbee Jul 07 '20 at 13:40
Agreed. Depends on what you want. Like Bob's trick.Thing I've learned from this is how flexibly "equations" and "inequalities" can be combined in Solve – PaulCommentary Jul 07 '20 at 14:56

1 Answers1