If cos O =-2/5 and tan O > 0 what is the value of sin O

negative square root 21 over 5.

Step-by-step explanation:

mathGiven that for an angle ,

We are to find the value of  

We know that

Cosine is negative in Quadrant II and Quadrant III.

Tangent is positive in Quadrant 1 and Quadrant III.

So, the given angle  lies in the Quadrant III.

We will be using the following trigonometric identity:

We have

Since the angle  lies in Quadrant III and sine is negative in that quadrant, so

Thus, option (B) is correct.

900 degrees

step-by-step explanation:

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15