how to find the radius when u r only give the perimeter and area of a segment?
To do this, you need to know what fraction the wedge represents, which should be given as part of the problem. Either the wedge is defined as being 1/6 or 1/8 or something like that, or the length of the arc segment will be given so that you can compare it to the perimeter to determine this.
For instance, if the perimeter is given as 40 and the arc is length 8, you know the area of that wedge represents 1/5th of the whole disc.
Multiply the area of the segment to work out the area of the whole circle. Then just plug your number into the formula of an area of a circle and solve for the radius. (Divide out pi to find r^2 and take the square root to get r.)