Trigonometry/Exercise: Chasing Angles
The Khan Academy has video material that walks through two very similar exercises to these, which you may find easier to follow:
The Angle Game 1
The angle is the same as the 56o angle, since the two lines marked with arrows are parallel and the line that crosses them must cross parallel lines at the same angle.
The angle is 180o-115o since it and the 115o angle add up to a straight line. So it is 65o.
We can now redraw the diagram with the angles as follows:
We have a triangle with angles x, 56o and 65o.
The Angle Game 2
There is an isosceles triangle with angles 75o, 75o and an unknown angle b. So
The angle 'c' is an angle in triangle . The other two angles are 30o and 101o.