mass number is defined as sum of number of protons and neutrons
so here for Isotope A
Isotope A contains 56 protons and 80 neutrons.
Mass number will be given as

For Isotope B
Isotope B contains 55 protons and 81 neutrons.

For Isotope C
Isotope C contains 57 protons and 80 neutrons.

For Isotope D
Isotope D contains 56 protons and 74 neutrons.

<em>So here Isotope A and Isotope B has same mass number</em>
Answer:
It is virtual and behind the mirror
Explanation:
When an image is produced by a mirror, we have the following situations:
- The image is said to be in front of the mirror if it is on the same side of the object, with respect to the mirror
- The image is said to be behind of the mirror if it is on the opposite side of the object, with respect to the mirror
Moreover:
- The image is said to be real if it is in front of the mirror
- The image is said to be virtual if it is behind the mirror
In this case, the image (located at point I) is on the opposite side of the object (located at point O), so it is virtual and behind the mirror.
Answer:
can you please translate to english?
Explanation:
The answer:
the full question is as follow:
<span>A Texas rancher wants to fence off his four-sided plot of flat land. He measures the first three sides, shown as A, B, and C in Figure below , where A = 4.90 km and θC = 15°. He then correctly calculates the length and orientation of the fourth side D. What is the magnitude and direction of vector D?
As shown in the figure,
A + B + C + D = 0, so to find the </span>magnitude and direction of vector D, we should follow the following method:
D = 0 - (A + B + C) ,
let W = - (A + B + C), so the magnitude and direction of vector D is the same of the vector W characteristics
Magnitude
A + B + C = <span> (4.90cos7.5 - 2.48sin16 - 3.02cos15)I</span>
<span>+ (-4.9sin7.5 + 2.48cos16 + 3.02sin15)J
</span>= 1.25I +2.53J
the magnitude of W= abs value of (A + B + C) = sqrt (1.25² + 2.53²)
= 2.82
the direction of D can be found by using Dx and Dy value
we know that tan<span>θo = Dx / Dy = 1.25 / 2.53 =0.49
</span>tanθo =0.49 it implies θo = arctan 0.49 = 26.02°
direction is 26.02°
I believe the coma is formed from the dust and gas from a comet.
Hope this helps!! :)