Answer:
a) We have an aspect ratio of 4:3
This means that the width of the screen, W, is about 4/3 times the height of the screen, H.
Then we have the equation:
W = (4/3)*H
And the diagonal of a rectangle with width W and height H is:
D = √(W^2 + H^2)
Then if we have a 15 in TV, then we have D = 15 in.
Then we have:
15 in = √(W^2 + H^2)
Now we can use the relation W = (4/3)*H and replace this in the above equation:
15 in = √(((4/3)*H)^2 + H^2)
Now we can solve this for H:
15in = √( (16/9)*H^2 + H^2)
(15in)^2 = (16/9)*H^2 + (9/9)*H^2 = (25/9)*H^2
(9/25)*(15in)^2 = H^2
√( (9/25)*(15in)^2) = H
(3/5)*(15in) = H = 9 in
The height is 9 inches, and the width will be:
W = (4/3)*9in = 12in.
Now let's do the same for a 42 in tv.
We can use the same equation than before, this time we get:
42 in = √(((4/3)*H)^2 + H^2)
We can do the exact same procedure as before, and we will get:
(3/5)*(42in) = H = 25.2 in
Then the width is
W = (4/3)*H = (4/3)*25.2in = 33.6 in
b) Now we do the same, but now we have the relation:
W = (16/9)*H
Then if D is the diagonal, we have the equation:
D = √(W^2 + H^2) = √( ((16/9)*H)^2 + H^2)
This time we can simplify it for any general D.
D^2 = (16/9)^2*H^2 + H^2
D^2 = (256/81)*H^2 + H^2 = (256/81)*H^2 + (81/81)*H^2
D^2 = (337/81)*H^2
(81/337)*D^2 = H^2
√( (81/337)*D^2) = H
(9/18.36)*D = H
Then if we have a 42 in TV, the height is:
(9/18.36)*42in = H = 20.59 in
And the width will be:
W = (16/9)*H = (16/9)*20.59in = 36.60 in
If we have a 60 in TV, we get:
(9/18.36)*60in = H = 29.41 in
And the width will be:
W = (16/9)*H = (16/9)*29.41in = 52.29 in
c) if all the aspect ratios are always exactly 16:9, then no, the width and height should be exactly the same for all the TV with that ratio.