Answer:
The measure of angle CDA is 
Step-by-step explanation:
see the attached figure to better understand the problem
we know that
In the right triangle ABF
Applying Pythagoras Theorem



In the right triangle CED


so

substitute the values


1. x+5y=8
2x- 5y=1 What you do is find the number/variable that are the same( here is is the +5y and -5y. You want them to be opposites(-,+) so that they cancel each other out. if they are not opposites, then multiply one equation by a negative sign to change it. Cross out the 5y's. Now you can combine like terms-x+2x=3x, and 8+1=9, so now your equation will look like this:
3x=9
x=9/3
x=3
now take x=3 and plug it into the first equation to solve for y. x+5y=8, so 3+5y=8
5y=8-3
5y=5
y=5/5
y=1
(3,1) are your answers.
now do the same with the other problems.
Answer:
A, B & C form the vertices of a triangle.
∠ CAB = 90°, ∠ ABC = 73° and AB = 9.4.
Calculate the length of BC rounded to 3 SF
If

then by the product rule,

and by the chain rule,

which leaves us with

Alternatively, if you exclusively want to use the chain rule, you can carry out logarithmic differentiation:

By the chain rule, differentiating both sides with respect to <em>x</em> gives

Solve for <em>f'(x)</em> yields

just as before.