+0

help plz

0
72
2
+21

What is the lateral area of this regular octagonal pyramid?

A. 84.9 cm^2

B. 120 cm^2

C. 169.7 cm^2

D. 207.8 cm^2

arota21  May 23, 2017

#1
+4172
+1

The sum of the areas of all 8 triangles is the lateral area.

And, each of these triangles are the same size.

So...

lateral area = 8 * area of one of these triangles

lateral area = 8 * (1/2) * base * height

From the Pythagorean theorem:

62 + 62 = height2          $$\rightarrow \quad \text{height} = \sqrt{72}=6\sqrt2$$

lateral area = 8 * (1/2) * 5 * 6√2

lateral area = 120√2     ≈     169.7   cm2

hectictar  May 23, 2017
Sort:

#1
+4172
+1

The sum of the areas of all 8 triangles is the lateral area.

And, each of these triangles are the same size.

So...

lateral area = 8 * area of one of these triangles

lateral area = 8 * (1/2) * base * height

From the Pythagorean theorem:

62 + 62 = height2          $$\rightarrow \quad \text{height} = \sqrt{72}=6\sqrt2$$

lateral area = 8 * (1/2) * 5 * 6√2

lateral area = 120√2     ≈     169.7   cm2

hectictar  May 23, 2017
#2
+75344
+3

The lateral  area will be comprised of 8 congruent triangles

The slant height  of each triangle  = sqrt (6^2 + 6^2)  = sqrt (72)  = 6sqrt (2) cm

And the base of each triangle  = 5 cm

So.....the total lateral  area  =

8 * (1/2) (base) (slant height)  =

8 (1/2) (5) (6sqrt(2) ) ≈  169.7 cm ^2

CPhill  May 23, 2017

19 Online Users

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details