Sector AOB is a sector of a circle. A student's attempt to find the area of sector AOB is shown below.

Identify the mistake made by the student.
Write out a correct solution.
69 exam-style questions on Edexcel A Level Maths Radians, covering 5.1 Radian Measure, 5.2 Arc Length, 5.3 Areas of Sectors and Segments, 5.4 Solving Trigonometric Equations, and 5.5 Small Angle Approximations. Each one has a worked solution and a mark scheme showing where the marks go.