Question

Pls answer this question
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Answer 1

Given:
A is a null matrix.

To Find:

Value of α

Solution:
According to Google, The determinant of a null matrix is equal to zero which means that the determinant of A should also be zero.

det(A)=0
Now we find the det(A) and we obtain the following equation
(cosα)(cosα)-(sinα-1)(1-sinα)
=cos²α -( sinα -sin²α-1+sinα)
= cos²α+sin²α+1-2sinα
We use the identity
cos²θ+sin²θ=1
= 1+1-2sinα
=2-2sinα
det(A)=0
2-2sinα=0
→ -2sinα=-2
→ sinα=1
∵ sin(90)=1

→α=90