ANSWER
EXPLANATION
The given trigonometric equation is
We factor cos(x) to get:
Apply the zero product property to obtain:
Using the unit circle,
when
and
We know
when
The sine function is negative in the third and fourth quadrants.
Hence the solutions are:
Consider the attached figure. If AB has length 1, then BC has length sin(15°) and CD (the altitude of triangle ABC) has length sin(15°)·cos(15°).
By the double angle formula for sin(α), ...
... sin(2α) = 2sin(α)cos(α)
Rearranging, this gives
... sin(α)·cos(α) = sin(2α)/2
We have
... CD = sin(15°)·cos(15°) = sin(2·15°)/2
... CD = sin(30°)/2 = (1/2)/2 = 1/4
That is, the altitude, CD, is 1/4 the hypotenuse, AB, of triangle ABC.
Answer : option d
4.4, 5.8, 7.2, 8.6, 10, …
First we find the common difference between two terms
5.8 - 4.4 = 1.4
7.2 - 5.8 = 1.4
8.6 - 7.2 = 1.4
10 - 8.6 = 1.4
So common difference is 1.4
To find recursive rule, we add the difference with previous term
Recursive rule is
a1 is the first term so a1= 4.4
d is the difference = 1.4
So recursive rule is
, where a1 = 4.4