Answer:
Identity is verified.
Step-by-step explanation:
We have to verify the identity 
To prove any identity we always prove one side(either left hand side or right hand side) of the equation equal to the other side.
In this identity we take the left hand side first
(as we know cos(a+b) = cosa×cosb-sina×sinb)
= - sinx ( Right hand side)
Hence identity is proved.
Observation one
From the markings on the diagram <1 = 60o The left triangle is at least isosceles. Therefore equal sides produce equal angles opposite them.
Now we have accounted for 2 angles that are equal (each is 60 degrees) and add up to 120 degrees. The third angle (angle 2) is found from this equation.
<1 + 60 + <2 = 180 degrees. All triangles have 180 degrees.
60 + 60 + <2 = 180
Observation 2
<2 = 60 degrees.
120 + <2 = 180
m<2 = 180 - 120
m<2 = 60 degrees.
Observation 3
m<3 = 120
<2 and <3 are supplementary.
Any 2 angles on the same straight line are supplementary
60 + <3 = 180
<3 = 180 - 60
<3 = 120
Observation 4
m<4 = 40 degrees.
All triangles have 180 degrees. No exceptions.
m<4 + 20 +m<3 = 180
m<4 + 20 + 120 = 180
m<4 + 140 = 180
m<4 = 180 - 140
m<4 = 40
Answer:
x=-1
Step-by-step explanation:
