integer value of triangle

how many integer values of z are there so that z, 4, and 7 could be the lengths of the sides of a triangle?

It is an explanation for finding the integral by the method of summation or by evaluating the integral as limit of a sum(part 3). Find by the method of summation the value of: ∫ sin xdx, where the lower limit is 0 and the upper limit is (1/2)π, i.e., integral of sin x, where the lower limit is 0 and the upper limit is (1/2)pi.

Calculus Integral Calculus(III) Definite Integral as the Limit of a sum Method of Summation Definite Integral It is an explanation for finding the integral by the method of summation or by evaluating the integral as limit of a sum(part 3). Find by the method of summation the value of: ... click for more

Perimeter of an octagon within a circle.

I need help with this one. Maybe I'm just reading to much in to the question, but I can figure this one out. Please help. A regular octagon is inscribed in a circle of radius 15.8 cm. Find the perimeter of the octagon.

Are eight points in a plane concurrent?

1. Eight points, A, B, C, D, E, F, G, and H are distributed in a plane. Exactly five of the points are on line l1, exactly three are on line l2, and exactly three are on line l3. Are the three lines concurrent? Justify answer.

Circle construction.

2. Given a circle, construct a circle with twice its area. I know that the r2 = (x-h)2 + (y+k)2 is the standard equation for a circle. I don't know how to use this formula to construct two circles where one is twice the area of the other. Please see attached.