Kézi írás egy krétával egy bonyolult matematikai egyenlet egy képlet egy táblára - Stock felvétel és videó

Colorful chalk drawing: the word Peace written in chalk on a black chalkboard

Hand writes with chalk I love you on blackboard.

Closeup shot of a chalkboard, somebody is writing cafe latte, cappuccino, espresso on it

Hand writing i miss you with white chalk on blackboard.

Gauss-Bonnet's formula. In that specific case this formula connects the local characteristic of a surface under the name Gaussian curvature and its global, topological characteristic quantity of through holes.

Female hand writing with chalk on chalkboard simple mathematical equation, a plus b equals c

Formula of trigonometry written mathematical formula with chalk on blackboard

Chemistry elements in one formula written on blackboard. Close up

Writing a trigonometric formula on the blackboard with white chalk

Female hand wipes chemical formulas with a rag

Correction of mistakes in the written formula on the blackboard with chalk