So, V_(ab)= V∟30⁰degree,V_(ab)case it is line to line voltage this line to line voltage leading this your yourwhat you call this voltage V_(an) by 30 Similarly, V_(bc) that is your V_(bc) actually from V_(an) it is lagging by 90 degree that is why V_(bc) is equal to it is line to line voltage.
इसी प्रकार, V_(bc)_(,) यह V_(bc) है जो वास्तव मे V_(an) से आपका 90 डिग्री(degree) से पिछड़ रहा है यही कारण है कि V_(bc) इसके बराबर है लाइन से लाइन वोल्टेज(line to line voltage)।