Doubt in circular motion

90 degrees?

At any general \theta find the velocity by energy conservation, then find a_c (centripetal) and a_{net} (resultant of tangential and centipetal accn.). Make angle between a_c and a_{net} = 45 degrees. You will get \theta.

PS. Don't have paper to solve rn.

Final answer g(1+root2) i forgot to remove m in first solution and
Forgot to remove l i second solution.To my view g(1+root2) is
Answer

Sir here angle made by string with vertical is asked. Pls check the question

Ok i misunderstood the language...let me try