Hint: Plot a graph between angles on x axis and voltage or variable on y axis.
Complete step by step solution:
1). If you plot the graph as angles on x-axis and respective variable (voltage or current) on y-axis, you will observe that wave A is 15 degrees before that of wave B.
2). (60-45=15) A leads wave B by 15.
3). A reach to 0 before B at 15 degrees
4). We find that a start from 45 and after 15 means at 60 b will start then it is clear that a is lead with 15.
5). Therefore, the correct option is A
Additional information: A sine wave is a geometric waveform that oscillates (moves up, down or side to side) periodically, and is defined by the function y=sinx. In other words, it is an s-shaped smooth wave that oscillates above and below zero. The sine wave as a technical chart analysis tool is based on advanced mathematics and is designed to indicate whether a market is trending or in a cycle mode.
Note: Before being able to solve the given sum, students need to be able to understand the concept of a sine graph. Also, they need to be able to understand how one graph leads or lags behind another graph.