00:01
Hello, in the question we have given three cables a, b and c are attached to a hook.
00:07
So these are the three vectors a, b and c.
00:11
So r is the resultant which is given in the question.
00:14
So we have to determine the magnitude of this vector b and this angle phi.
00:20
So now in order to do this we will use the, we will see the horizontal components.
00:30
So we will have horizontal components of vectors.
00:42
So now if i drop a perpendicular over here, so of a, so i will see, note that this a will be pointing in the negative x direction.
00:54
So it will be, and this magnitude will be a cos of 20.
00:59
So this, if i just drop over here, if i make this triangle, so now this is the right angle triangle which i am considering.
01:06
Now this side i can use the trigonometric identities and i will note that this will be minus of a cos of 20 degrees.
01:18
Then i will have this c.
01:21
So now c also, if i drop this perpendicular over here like this, so this will be sin phi.
01:30
So c sin phi.
01:32
This is the right angle triangle which i am considering and this vectors i can translate.
01:37
So i can translate it over here and i can see that the c is going in the x direction.
01:42
So this will be c sin of phi that is equal to minus r.
01:50
So in the same way, if i take the projection of this r along this, so i will get this r sin of 23.
02:02
Now let us plug the value.
02:04
A, we know what it is.
02:05
A is 65 cos of 20 plus c, we know it is 40 sin of phi that is equal to minus r is 100 sin of 23.
02:23
So if i calculate this, so i will get sin of phi.
02:29
So that is equal to minus of 100 sin of 23 is minus of 39 .07 and then this i will bring over here.
02:40
So it will become plus 65 cos 20 degree is 61 .08 divided by this 40.
02:50
So i will get sin phi as equal to 0 .55025.
03:01
So phi will be equal to sin inverse of this 0 .55025.
03:13
So now if we calculate, so this angle phi, we will get it as 33 .4 degrees.
03:22
So this is the first part...