Posted by **Kate** on Sunday, April 29, 2007 at 3:19pm.

The area of a regular pentagon with a perimeter of 35 units.

Join the centre to each vertex to form 5 eq

Join the centre to each vertex to form 5 equal triangles. Consider one of those triangles

the central angle is 72º and each of the other two equal angles is 54º, and the base is 7 units.

Can you find the height of that triangle using simple trig?

then the area of the triangle is 1/2 base*height

Multiply that answer by 5.

I am not sure what the formula is for the height in my Trig book it says H=a sin 0... but i dont know what a is equal to.

O never mind sorry i was making the problem to hard then what it was

I would use tangent

let the height be h

then tan 54=h/3.5

h=3.5*tan54

=4.817

the formula your book uses requires the hypotenuse of the right-angled triangle.

O i did sin 36/3.5 =sin54/c

then a= .5(7)(4.8)= 16.8 units^2

then times 16.8*5=84ft squared

good, I had the same answer (84.3)

## Answer This Question

## Related Questions

- Math - This regular octagon has a side length 15.0cm. Determine the distance ...
- Math - Find the area of a regular pentagon if its apothem is approximately 4 ft ...
- Geometry - Regular pentagons A and B are similar. The apothem of Pentagon A ...
- TO REINY - I don\'t follow your thinking If the do, it is an easy problem. draw ...
- math - louis drew all of the possible diagonals from one vertex of a regular ...
- geometry - 1. An exterior angle of a regular polygon measures 30 degrees. What ...
- Geometry - A regular pentagon has side length 12cm.the perimeter of the pentagon...
- Math--Area - Find the area of each regular polygon to the nearest tenth. Octagon...
- Algebra 2 - Hey I am working on math homework that involves "Standard Form to ...
- math-10th grade( quadractics) - the centre point of a circle is 5,3. the top ...

More Related Questions