Interim President of the Constituent Assembly
The interim President of the Constituent Assembly in its first meeting held on December 9, 1946, was Sachchidanand Sinha.

Sachchidanand Sinha
Sachchidanand Sinha was a prominent Indian politician and a key figure in the Indian independence movement. He was born on January 10, 1871, in Arrah, Bihar. Sinha was a lawyer by profession and had a deep interest in politics. He actively participated in the freedom struggle and played a crucial role in shaping India's political landscape.

Role in the Constituent Assembly
Sachchidanand Sinha was one of the founding members of the Constituent Assembly of India. The Constituent Assembly was established to draft and enact the Constitution of India. It was formed after the elections held in 1946 to the Provincial Legislative Assemblies, where members were elected by the members of the newly formed provincial assemblies.

First Meeting of the Constituent Assembly
The first meeting of the Constituent Assembly was held on December 9, 1946, at the Constitution Hall in New Delhi. The purpose of this meeting was to elect the interim President of the Constituent Assembly, who would preside over its sessions until a permanent President was elected.

Selection as Interim President
During the first meeting of the Constituent Assembly, Sachchidanand Sinha was chosen as the interim President. His selection was a result of his reputation, leadership qualities, and his significant contributions to the freedom struggle. Sinha's vast experience in law and politics made him a suitable candidate for this prestigious position.

Conclusion
Sachchidanand Sinha's appointment as the interim President of the Constituent Assembly highlights his importance in the Indian independence movement and his significant role in shaping the Constitution of India. His leadership during the initial stages of the Constituent Assembly set the stage for the drafting and enactment of the Constitution, which remains the guiding document of India's democracy.