If the lengths of the two sides of the triangle are 5cm and 12cm respectively, then the third side is the root of the equation x ^ 2-30x + 221 = 0. What is the circumference of the triangle?

If the lengths of the two sides of the triangle are 5cm and 12cm respectively, then the third side is the root of the equation x ^ 2-30x + 221 = 0. What is the circumference of the triangle?

That is 12-5

A triangle with an area of 275 square centimeters and a height of 11cm. How much is the bottom? I want the equation and the formula

Triangle formula s = ah / 2
275=11a/2
Solve the equation a = 50
So the bottom is 50cm

The area of a triangle formed by the three central lines of a triangle with an area of 16 cm and 178
And the reasons are briefly described

Let ABC be the triangle, and PQR be the triangle whose middle line is the edge,
Then s △ PQR = s △ ABC (3 / 4) = 16 * 3 / 4 = 12cm ^ 2
Let ABC be a triangle, and let ad, be and CF intersect at G,
Extend GD to m, so that DM = GD connects MB and MC,
The quadrilateral bgcm is a parallelogram,
BG=CM,GM=2GD=AG,
BD=CD,
S△GCM=2S△CDG,
S△ABD=S△ADC=S△ABC/2,
According to the nature of the center of gravity,
AG=2DG,
S△CDG=S△AGC/2==S△ADC/3=S△ABC/6,
S△GCM=S△ABC/3,
GC/CF=MC/BE=GM/AD=2/3,
The triangle with three midlines as sides is PQR,
△GMC∽△PQR,
S△GMC/S△PQR=（2/3)^2=4/9,
S△PQR=9S△GMC/4,
∴S△PQR=(9/4)*S△ABC/3=3S△ABC/4.