If angle 2 measures 155 degrees in the image below, what is the measurement of angle 1?

diagram of truss with some angles missing

What are the measures of the angles located at positions a, b, & c? Note: the figure is symmetrical on the vertical through angle b.

The large triangle is an isosceles triangle. The two angles on the base are equal.Angle a = 35°

We now know two angles in the largest triangle. The third angle, angle b must add to these to make 180°.  

35° + 35° + b = 180°

b = 180° - 70°

b = 110°

We now know two angles in a quadrilateral. The two unknown angles, including angle c are equal. All four angles add up to 360°.  

2c + 110° + 120° = 360°

2c = 360° - 230°

2c = 130°

c = 65°

Step-by-step explanation: