a+b+c=0
a+b=-c
|a+b|=|c|
a²+b²+2abcos∆=|c|²
1+1+2cos∆=1
cos∆= -1
∆=π
Hello Dileep, I am glad to help you.
9+25+30cos∆=49
cos∆=1/2
∆=π/3 = 60°
I think your doubt is clear now.
All the best.
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