Previous-year question practice database
Answer
Exam answer
sin A [[sin A, −cos A],[cos A, sin A]] + cos A [[cos A, sin A],[−sin A, cos A]]
= [[sin²A, −sinAcosA],[sinAcosA, sin²A]] + [[cos²A, sinAcosA],[−sinAcosA, cos²A]]
= [[1,0],[0,1]].
Answer: [[1,0],[0,1]].
Explanation
Multiply each matrix by its scalar, add corresponding entries, and use sin²A+cos²A=1.