Sorry for a basic question but I really wanted to understand the relation between the instantaneous frequency and instantaneous phase of a sinusoid. We know that we can get the the instantaneous frequency by differentiating the instantaneous phase and normalizing with 2*pi. Also, we could get the instantaneous phase by integrating the frequency. But i am not quite understanding how integrating a frequency gives instantaneous phase. I viewed this link - http://mriquestions.com/phase-v-frequency.html. The total area under the graph of Instantaneous frequency gives phase but how to interpret it practically?
For example, if I consider a sinusoid whose frequency is 10Hz and is constant for 10 seconds , it gives me total area as 100. Another sinusoid with 10Hz for 5 seconds and 20Hz for 5 seconds, gives a total area of 150. How these numbers (areas) can be interpreted as phase?