Math Is Fun Forum
Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °
You are not logged in.
- Topics: Active | Unanswered
#1 2007-10-25 07:11:40
- xXxEmZyxXx
- Member
- Registered: 2007-10-15
- Posts: 12
functions
F(x)=5sin(2x)-2cosx
is this funtion R->R
injective, surjective, or both anyone know and can show me how to determine for future references
Offline
#2 2007-10-25 07:31:18
- JaneFairfax
- Member
- Registered: 2007-02-23
- Posts: 6,868
Re: functions
It is a function from
to .It is not injective because e.g.
It is not surjective because the maximum value of 5sin2x is 5 and the meximum value of −2cosx is 2, so their sum isnt going to exceed 7 hence there is no x such that F(x) = 8.
Offline
#3 2007-10-30 06:21:46
- xXxEmZyxXx
- Member
- Registered: 2007-10-15
- Posts: 12
Re: functions
thanks but what properties of sine/cosine did you use to get the values of x???
Offline