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Suppose that sin(t) = − 3/ 5 and is in quadrant 4. Find the following:
(a) cos(t) =

(b) sin(2t) =

(c) cos(2t) =

(d) tan(2t) =

(e) The quadrant of the angle 2t.

(f) The quadrant of the angle 1/ 2 t.

(g) sin 1 /2 t =

(h) cos 1 2/ t

Sagot :

Answer:

see below

Step-by-step explanation:

As sin(t) = -3 / 5 and in quadrant 4

so cos is positive

a) sin^2(t) + cos^2(t) = 1

(-3/5)^2 + cos^2(t) = 1

cos^2(t) = 1 - (9/25)

cos^2(t) = (25 - 9) / 25 = 16/25

cos(t) = +4/5

b) sin(2t) = 2 sin(t)cos(t)

= 2 * (-3/5) * (4/5)

= -24/25

c) cos(2t) = cos^(t) - sin^2(t)

= (4/5)^2 - (-3/5)^2

= 16/25 - 9 / 25

= 7 / 25

d) tan(2t) = sin(2t) / cos(2t)

= (-24/25) / (7/25)

= -24/7

e) as sin(2t) is negative and cos(2t) is positive

2t is in Quadrant 4

I am not sure for below three

f) cos(t) = cos^2(1/2 t) - sin^2(1/2 t) = 4/5

  cos^2(1/2 t) + sin^2(1/2 t) = 1

by adding and solving

1 + 4/5 = 2 * cos^2(1/2 t)

9/10 = cos^2(1/2 t)

cos(1/2 t) = +- 3/[tex]\sqrt{10}[/tex]

and sin(t) = 2 * sin(1/2 t) * cos(1/2 t) = -3/5

2 * sin(1/2 t) * 3/sqrt{10} = -3/5

sin(1/2 t) = +- 1/sqrt{10}

means here sin and cos for 1/2 t should be opposite signs

so it is either 2nd or 4th quadrant

g) sin( 1/2 t) = +-1/sqrt{10}

h) cos(1/2 t) = +- 3/sqrt{10}