5
If tan θ = —— , calculate the value of cos θ:
4
Recall the definition of the tangent function:
sin θ
tan θ = ————
cos θ
5 sin θ
—— = ————
4 cos θ
Cross multiply:
5 · cos θ = 4 · sin θ
Square both sides:
(5 · cos θ)² = (4 · sin θ)²
5² · cos² θ = 4² · sin² θ
25 · cos² θ = 16 · sin² θ
But sin² θ = 1 – cos² θ. Substitute that for sin² θ into the equation above, then you get
25 · cos² θ = 16 · (1 – cos² θ)
25 · cos² θ = 16 – 16 · cos² θ
Isolate cos² θ:
25 · cos² θ + 16 · cos² θ = 16
(25 + 16) · cos² θ = 16
41 · cos² θ = 16
16
cos² θ = ———
41
4²
cos² θ = ————
(√41)²
Take square root of both sides:
4
cos θ = ± ———
√41
4 4
cos θ = – ——— or cos θ = ——— ✔
√41 √41
The sign of cos θ depends on which quadrant θ lies. Since you first have a positive value for tan θ, then that means θ lies either in the 1st or the 3rd quadrant.
• If θ is a 1st quadrant angle, then
cos θ > 0
4
cos θ = ——— ✔
√41
• If θ is a 3rd quadrant angle, then
cos θ < 0
4
cos θ = – ——— ✔
√41
I hope this helps. =)
Answer:
If the bathtub was full it made a splash and got wet if the bathtub was empty if hit the bottom and bounced
Step-by-step explanation:
Answer:
89°
Step-by-step explanation:
It is the first of a new study from the University of ÷|gsuj the most of the world the first time in a long time and money on what will happen in a way that would have to be careful about the future of this is to proa vide make be the it
Answer:
x = 4
Step-by-step explanation:
We can use cross products to solve
84/12 = 28/x
84 * x = 12 *28
Divide each side by 84
84x/84 = 12*28/84
x =4
Time taken for Kristin to catch up with the truck will be found using the formula
time=(distance)/(speed)
distance=20 km
speed=90 km/h
thus
time=20/90=2/9 hours
Answer: 2/9 hours
