Trigonometric Formulas, Identities and Equation

[palui123]

Homework Statement

t = tetha

FInd sin 2t when cos t = 4/5

Homework Equations

no idea

The Attempt at a Solution

no. . . . btw what should I do 1st? I don't understand this question

 

[eumyang]

1) You are given that cos t = 4/5. Can you find sin t?
2) Do you know your trig identities? Particularly the double-angle formulas.

 

[HallsofIvy]

Homework Statement

t = tetha

FInd sin 2t when cos t = 4/5

Homework Equations

no idea

The Attempt at a Solution

no. . . . btw what should I do 1st? I don't understand this question

Exactly what part of "Find sin 2t" do you not understand?

 

[palui123]

Formula:
Sin2t = 2 sint costWhat I do is:
Sin2t = 2sint cost

since cost = 4/5

sin2t = 2sint (4/5)

sin2t = 8sint/5

What should I do then..? I know its wrong

 

[palui123]

w8. . . nvm. I know how to this question now.

sin 2t = 2 sint cost

since cost = 4/5 ,

a=4 , h=5 , o=??

P.theorem:
a^2=b^2+c^2
o=3

then sint = 3/5

then subtitude =D . . . solve get the answer. . .I'm talking by myself T-T ask = me , answer = me T-T . AID ME NEXT TIME PLEASE. . . .

 

[eumyang]

I'm talking by myself T-T ask = me , answer = me T-T . AID ME NEXT TIME PLEASE. . . .

If by "aiding you" you mean, show you the work + answer, then NO, WE CAN'T DO THAT. Read the forum rules. Otherwise, I think I gave you sufficient aid in my post (#2).