We have a figure made of four right triangles.
Now, we need to find the missing sides for each triangle to get the side x.
Let's use the triangle ABE:
AB represents for this triangle the adjacent side and we need to find the
opposite side BE.
To find the value for BE, we need to use trigonometric functions. The functions must involve the side that we know and the side that we want to find. Therefore:
Tan = opposite side/ adjacent side
Replacing the values:
Tan 45 = BE/AB
Tan 45 = BE/ 10in
Solve for BE:
BE = Tan 45* 10in
BE = 10in
Now, for triangle BEF:
BE represents the adjacent side and BF the hypotenuse.
Therefore, we use the next trigonometric function
cos = adjacent side/ hypotenuse
Replacing the values:
Cos 60 = BE/ BF
Cos 60 = 10/ BF
Solve for BF
BF = 10/Cos 60
Then
BF = 20in
Now, for triangle BFC:
The angle B is equal to 180. We have a right angle and an angle of 60 degrees. Therefore, for m∠B
m∠B = 90+60 + a = 180
Solve for a:
150 + a = 180-150
a = 30
Where a is the inside angle b for the triangle BEF.
In this triangle, BF represents the hypotenuse and we need to find the opposite side CF.
Hence, we use the next trigonometric function:
Sin = opposite side/ hypotenuse
Replacing the values:
Sin 30 = CF/BF
Sin 30 = CF/20
Solve for CF:
CF = 10 in
Finally, for triangle CFD:
CF represents the adjacent side and we need to find the hypotenuse DF = x.
Hence, we use the next trigonometric function:
Cos = adjacent side/ hypotenuse
Replacing the values:
Cos 30 = CF/x
Cos 30 = 10/x
Solve for x:
x = 10/Cos 30
Then:
Therefore, the correct answer is the third option.