Yes it is true:
(1 - cos^2 x) = sin^2 x Sqr.(1 - cos^2 x) = sin x and (-sinx) True, since sin x negative. Also, x terminates in quadrant 3 and 4. Hope this is helpful
Answer:

Step-by-step explanation:
From the question we are told that
System of equations given as
x₁ + 3x₂ + x₃ + x₄ = 3;
2x₁ - 2x₂ + x₃ + 2x₄ = 8;
x₁ - 5x₂ + x₄ = 5
Matrix form

Generally the echelon reduction is mathematically applied as

Add -2 times the 1st row to the 2nd row

Multiply the 2nd row by -1/8

Add -1 times the 2nd row to the 3rd row

Multiply the 3rd row by -8/41

Add -1/8 times the 3rd row to the 2nd row
Add -1 times the 3rd row to the 1st row

Add -3 times the 2nd row to the 1st row

The entire angle is a 90 degree angle.
Subtract the entire angle from what is given to find x.
90-28=62
x=62
Answer:
25/6 = 4 with a remainder of 1
When you have -(-2) it equals +2 and the same goes for any other number. When you have +(-2) it equals -2 and the same goes for any other number. Hope this helps!