18 19 20 please thank you

18a) The height of tree is 6.34ft.

Diagram We would scale a right side triangle showing side; 6.34ft x base 13.59ft x 15cm slope.

b) 11.54 degree

Step-by-step explanation:

18a) sin(25) = 0.4226182617 is what you multiply to check the height.

15 x 0.4226182617 = 6.339273926   = 6.34ft.

Using the measurements of pythagoras you can scale each measurement above.  6.34 = (x0.5) = 3.17cm to draw the trees height.

15ft wire = scale the diagram draw  1cm = 2ft So that 7.5cm =  = 15ft

Draw a right angle triangle and before creating the slope use protractor or guess 25 degree at bottom of slope and label it.

This will make a 7.5cm slope and label it 15ft.

We also measure out the base which on scale cm per foot is 13.59 x 0.5 = 6.80cm and label it 13.59ft.

We find the base measurement by finding the square of each 15 and 6.34

c^2 - a^2 = b^2

a= 6.34 x 6.34 = 40.1863939089 = √40.19

c = 15 x 15 =  √225

c-b = √225 - √40.19 =  √184.81

side = b  

b^2 = √184.81= 13.5944841756 = 13.59ft

18 b)  To find an angle x  with given measurements 4ft base and 20ft slope we  

use sin( base/slope) = (run/rise)

So that 4/20 = 0.2  

Then plug in for sin -1  0.2 = 11.54 degree = (calc ..11.53695903)

Notes;

If 4ft base was not given and the height of wall was given we would do the same using base as run and slant as run run/rise  but we would substitute sin-1 and after division run/rise we would plug in the decimal to cos-1 (decimal).