practice exam help? (1 Viewer)

[timinator1993]

ok so another part to the question is find sin 180+x (with sinx=0.725)
so
its -sinx, so its -0.725??

 

[random-1005]

ok so another part to the question is find sin 180+x (with sinx=0.725)
so
its -sinx, so its -0.725??

thats all it is, you can just derive them all from the circle,

 

[timinator1993]

thanks alot, the last part is find sin(-x),
so would it be -0.725???

 

[hscishard]

Yea

 

[timinator1993]

cool, thanks alot for your help and random too

 

[timinator1993]

ok, another question, for question 2a, i know than tanA=2.245, so to find all values between 0and360, would i just do 180+2.245, or do i need to find the shift tan of 2.245? my problem is i dont know when to do stuff, like how do i know that the tan of A is 2.245, or do i need to first find tanA??

 

[timinator1993]

ok, another question, for question 2a, i know than tanA=2.245, so to find all values between 0and360, would i just do 180+2.245, or do i need to find the shift tan of 2.245? my problem is i dont know when to do stuff, like how do i know that the tan of A is 2.245, or do i need to first find tanA??

scratch that, figured it out

 

[Omnipotence]

Are you serious?

 

[timinator1993]

Are you serious?

yes i am

 

[Existential]

For Question 2, part (d)

Solve 5cosx=3+2cosx (x for 0-360 degrees)

someone please answer and explain.

 

[random-1005]

For Question 2, part (d)

Solve 5cosx=3+2cosx (x for 0-360 degrees)

someone please answer and explain.

just normal eqn

3cosx=3
cosx=1

then grapically

x=0, 2pi i think thats it

 

[Existential]

AM I CRAZY???????

this question does not work!

Q3ai

Triangle ABC has sides AB=3cm, BC=6cm and CA=5cm.

Use the cosine rule to show that Angle BAC = 94 degrees.

I keep getting a negative answer - HELP!

 

[Omnipotence]

AM I CRAZY???????

this question does not work!

Q3ai

Triangle ABC has sides AB=3cm, BC=6cm and CA=5cm.

Use the cosine rule to show that Angle BAC = 94 degrees.

I keep getting a negative answer - HELP!

Maybe its an obtuse angle?

 

[Existential]

Maybe its an obtuse angle?

would that matter? (since the cosine rule is for non-right-angled triangles)

 

[Omnipotence]

would that matter? (since the cosine rule is for non-right-angled triangles)

Right.

 

[Existential]

Right.

I must be missing something. The second part is find the area of the triangle.

ANYONE?

 

[Omnipotence]

I must be missing something. The second part is find the area of the triangle.

ANYONE?

Area is 1/2a.b. sinC, it should work.

 

[random-1005]

Right.

its correct, if you get a negative answer for cos you are in 2nd quadrant, ie obtuse angle and it obviously cannot be a reflex as the sum of all angles of triangle equals 180, you cannot have one angle greater than the whole 180 .

cosx = (3^2 +5^2 -6^2) / (2(3)(5))

 

[Existential]

Area is 1/2a.b. sinC, it should work.

the cosine rule is getting me a negative answer!!!

and i need "sinC" before i can do area of triangle!!!

 

[random-1005]

the cosine rule is getting me a negative answer!!!

and i need "sinC" before i can do area of triangle!!!

no its not, when the do the calculation ignore the negative of the cos ( what would you do if i asked you to solve cosx= -1/2 for 0<x<360??) and find the related angle and then do 180- that angle

180- cos^-1 (1/15) is the angle