Phase Shift and Amplitude
y = A·sin(Bx+C)+D. Amplitude A, period 2π/B, phase shift -C/B, vertical shift D. Essential for waves, AC circuits, and signal processing.
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Phase shift -C/B: positive C shifts the graph left, negative C shifts right. sin(x + π/2) = cos(x) — cosine is sine with a 90° phase shift. In AC circuits, voltage and current can be out of phase — the phase difference matters for power.
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Why: Phase shift determines when a wave starts; amplitude is its height. Used in sound, light, AC circuits, and any periodic signal.
How: For y = A·sin(Bx+C)+D: A = amplitude, period = 2π/B, phase shift = -C/B (horizontal), D = vertical shift. Frequency f = B/(2π) in cycles per unit.
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Wave Parameters
Amplitude / Period / Shift
Wave Composition
Calculation Breakdown
For educational and informational purposes only. Verify with a qualified professional.
🧮 Fascinating Math Facts
Amplitude |A| is the maximum displacement from the midline. Period 2π/B is one full cycle.
— Wolfram MathWorld
Phase shift -C/B moves the graph horizontally. Positive C → left shift.
— Khan Academy
Key Takeaways
- • y = A·sin(Bx+C)+D — A=amplitude, B=frequency, C=phase (radians), D=vertical shift
- • Period = 2π/B; frequency in Hz = B/(2π)
- • Phase shift = -C/B (in x-units); in degrees: -C/B · 180/π
- • Positive C shifts the wave left; negative C shifts right
- • Essential for sound waves, AC circuits, signal processing
Did You Know?
How It Works
Amplitude (A)
|A| is the vertical stretch. The wave oscillates between +A and -A (before vertical shift). Negative A flips the wave.
Period and Phase
Period T = 2π/B. Phase shift in x-units is -C/B. Write as A·sin(B(x - h)) + D to see h = -C/B directly. Sine and cosine differ by π/2 phase.
Vertical Shift (D)
D moves the entire wave up or down. The midline is y = D. Range becomes [D - |A|, D + |A|]. See Sine Calculator.
Expert Tips
Factored Form
Write y = A·sin(B(x - h)) + D. Then h = -C/B is the phase shift. Easier to read from the graph.
Phase is Cyclic
Adding 2π to C gives the same wave. Phase shift is defined modulo the period. Use Unit Circle.
AC Circuits
In AC, phase difference between V and I affects power factor. Inductors and capacitors shift phase by 90°.
Sine vs Cosine
sin(x + π/2) = cos(x). They are the same wave with a 90° phase difference. Choose based on initial conditions.
Comparison: Wave Parameters
| Parameter | Effect | Formula | Units |
|---|---|---|---|
| A (Amplitude) | Vertical stretch | |A| | Same as y |
| B (Frequency) | Horizontal squeeze | 2π/B = period | rad/unit x |
| C (Phase) | Horizontal shift | -C/B | radians |
| D (Vertical) | Up/down shift | D | Same as y |
| Period | One full cycle | 2π/B | x-units |
| Phase (deg) | Shift in degrees | -C/B · 180/π | degrees |
| Freq (Hz) | Cycles per unit | B/(2π) | Hz |
| Midline | Center of wave | y = D | y-value |
Frequently Asked Questions
How does phase shift affect the wave?
Phase shift moves the wave horizontally. Positive C shifts left; negative C shifts right. The displacement in x-units is -C/B.
What is the difference between phase shift and vertical shift?
Phase shift moves the wave left/right (horizontal). Vertical shift (D) moves it up/down. They are independent.
Why is the phase shift -C/B and not C?
In sin(Bx+C), when Bx+C = 0, x = -C/B. So the "start" of the wave is at x = -C/B, which is a shift of -C/B units.
How do I convert phase shift from radians to degrees?
Multiply by 180/π. So phase_deg = (-C/B) · (180/π). A full period (2π rad) = 360°.
What happens when B is negative?
B should be positive for standard form. If B < 0, the wave reverses direction. Use |B| and adjust C.
Applications in signal processing?
Phase shifts are used in filters, modulation (AM/FM), coherent detection, and beamforming. Phase relationships determine interference.
How does amplitude affect the wave?
Amplitude |A| is the maximum displacement from the midline. It scales the wave vertically. Negative A reflects the wave.
What is the relationship between sine and cosine?
cos(x) = sin(x + π/2). They are the same wave with a 90° (π/2) phase difference. Choose based on where the wave "starts".
Phase Shift by the Numbers
Official & Educational Sources
Disclaimer: Results for educational use. For signal processing or AC circuit design, verify with domain-specific tools.
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