Question

What is the phase angle between

i₁ = -4 sin (377 t + 25°) and 

i2 = 5 sin (377 t + 40°)?

1. 155°, (i₁ leads i2) 
2. 145°, (i2 leads i1) 
3. 135°, (i1 leads i2) 
4. 125°, (i2 leads i1) 
5.

Answer 1

Correct Answer - Option 1 : 155°, (i₁ leads i2) 

option 1 is correct

i1 = -4 sin (377 t + 25°)

i₁ can we written as 

i₁=4cos(377t+25°+90°) because {cos(90+θ )= -sin(θ )}

i₁=4∠ 115° 

i2 = 5 sin (377 t + 40°)

i₂ can we written as 

i₂=5cos(377t+90°-40°) because cos(90-θ)= sin(θ)

i₂=5∠-40° 

i₁ leads i₂ by 155°