Let w = cos(x)
The given equation turns into -5w^2 + 4w + 1 = 0. Use the quadratic formula to find that the two solutions, in terms of w, are:
The solution w = 1 leads to cos(x) = 1 which then becomes x = 0, x = 2pi, x = 4pi, etc. The general way to write this is x = 2pi*n where n is any integer. These angles are in radian mode.
The solution w = -0.2 leads to cos(x) = -0.2 which becomes x = arccos(-0.2) = 1.77215 approximately assuming your teacher wants the angle in radian mode. Unfortunately, I don't know the exact value of x here. There may not be an exact value, or finding this exact value may be well beyond the scope of this course.
Answer:
the 3rd one
Step-by-step explanation:
//I take it you're trying to find the area or circumference of a circle, so I'll do both.
= area
3.14 * <span>
= 28.26 (2 d.p)
</span>2
r = circumfrence
<span>2 * 3.14 * 3 = 18.84 (2 d.p)</span>
