The RMS value of the voltage u(t) = 3 + 4 cos(3t) is

• A. 7
• B. 5
• C. 3 + 2(1.41)
• D. 4.12

Answer: (D)

if voltage is given by,
v(t) = V₀ + V₁ cos(3t) + V₂ cos(5t)+ …
RMS value is given by,
√( V₀² + (V₁/√2)² + (V₂/√2)² + …)