Video Transcript
Evaluate the determinant of
negative four eight sec 𝜃 negative sec 𝜃 two tan squared 𝜃.
Remember these lines represent the
determinant of the matrix. For the matrix 𝐴, given by 𝑎, 𝑏,
𝑐, 𝑑, its determinant is calculated by finding the product of elements 𝑎 and 𝑑
and subtracting the product of 𝑏 and 𝑐. Let’s apply this to the matrix
we’ve been given.
The determinant of 𝐴 is negative
four times two tan squared 𝜃 minus eight sec 𝜃 times negative sec 𝜃. We can simplify our expression to
get negative eight tan squared 𝜃 add eight sec squared 𝜃. We are next going to factorize our
expression to give us the determinant of 𝐴 equals eight multiplied by six squared
𝜃 minus tan squared 𝜃.
Then, in order to take this
further, we do need to recall our trigonometric identities. The one we’re interested in today
is tan squared 𝜃 add one equals sec squared 𝜃. Let’s rearrange this formula to get
sec squared 𝜃 minus tan squared 𝜃 equals one. We’ve done this so we can replace
sec squared 𝜃 minus tan squared 𝜃 with one in our expression, leaving us with the
determinant of 𝐴 equals eight times one which is eight.
The determinant of our matrix is
eight.
