This document discusses strain and angles in engineering. It states that the tangent of an angle θ can be approximated as θ in radians if the angle is very small. It also states that the complementary angle θ' of an angle θ is equal to θ when measured in radians. Finally, it distinguishes that normal strain only causes a change in volume while shear strain only causes a change in shape.

1. γ = tan θ = δ/ y ≅θ in radians provided that θ is very small
γ = π/ 2 - θ’ = θ (in radians)
Normal strain causes only a change in volume. on the other hand,
shear strain causes only change in shape.
θ’