For area of circle we can use this three steps :
sector of a cicle = πr²θ/360°
Put θ=90°
Finally ,Area of Quadrant of a circle=πr²×90°/360°=(πr²)/4
Example:- If radius of circle, r=7 cm
Then area of Quadrant=πr²/4
={(22/7)×7×7}/4
={(22×7×7)}/7×4
=(11×7)/4
=(77/4) cm²