Question

Please solve question 10

Answer 1

cos A - sin A = 1

(cos A - sin A)² = 1²

cos²A -2.cos A.sin A + sin²A =1         [(a-b)²=a²- 2ab +b²]

1 - 2.cos A.sin A = 1                            [sin²A + cos²A = 1]

-2.cos A.sin A = 0

2.cos A.sin A = 0

adding 1 on both sides

2.cos A.sin A + 1 =0 + 1

cos²A +2.cos A.sin A +sin²A = 1

(cos A + sin A)² = 1                           [a²+2ab+b² = (a+b)²]

√(cos A + sin A)² = √1

cos A + sin A = ±1