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Maths question trig?

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I still dont understand could you explain what you are talking about i.e why its tan? Put examples in

Okay, right. Let's start from the beginning.

What can you tell me about angles BDA and CAD? And can you give me the size of one of these angles?

Reply 21

shutupem

Original post by Forevereuphoria

How are you labelling the sides...
is the answer 90

The sides are labelled by their letters, so AC is the side between letters A and C

it can't be 90, the diagonals of a rectangle don't intersect at right angles, it would have to be a square for that to happen.

(edited 9 years ago)

Reply 22

Forevereuphoria

Original post by Slowbro93

Okay, right. Let's start from the beginning.

What can you tell me about angles BDA and CAD? And can you give me the size of one of these angles?

They are all the same?

Reply 23

Forevereuphoria

Can someone tell me the answer and as its a hw game im doing and i'll speak to my teacher tomorrow

Reply 24

Slowbro93

Original post by Forevereuphoria

They are all the same?

Yes, so now what is the angle? you have two lengths, how can you calculate it?

And no, we will not tell you the answer but we can assist you.

Reply 25

Forevereuphoria

Original post by Slowbro93

Yes, so now what is the angle? you have two lengths, how can you calculate it?

And no, we will not tell you the answer but we can assist you.

Times 14 and 18 ??? i dONT KNOW

Reply 26

jaker3278

Ok look at triangle B-A-D its a right angle triangle that has an area of half the square. Now look at the other information you are given the length C-D = 14cm and A-D = 18cm. What else can we see, we can see that the triangle the angle x is in is and equilateral triangle. Ok we need to use this information to find the the angle x. First you need to do some trigonometry to find the angle at B with in the triangle with the angle x.(its hard to describe without a drawing) . SOHCAHTOA right, so we need TOA because we know the opposite length and the adjacent length. Tan X = 18/14 . then answer divided by Tan and we have the angle B of the triangle B-A-D. Now that we have that and we also know that the angles within a triangle add up to 180. so the triangle with x in it has two angles that equal B and one that equals X. so the next calculation is 180-(B*2) and that will give you the angle X.

Reply 27

Slowbro93

Original post by Forevereuphoria

Times 14 and 18 ??? i dONT KNOW

Have you not done SOH CAH TOA?

Reply 28

narcotica

Haa mymaths :biggrin:

15.4183541cm
(15.4cm to 3sf.)

Reply 29

Forevereuphoria

Original post by Slowbro93

Have you not done SOH CAH TOA?

could i do toa
and
18/14=0.28
then
tan-1(0.28)=
52.1

Reply 30

Forevereuphoria

Image is attached

(edited 9 years ago)

Reply 31

jaker3278

Hi what part are you stuck on with this question. do you know how to start it?

Image is attached

Have a good read of this it will tell you how to do it,

Ok look at triangle B-A-D its a right angle triangle that has an area of half the square. Now look at the other information you are given the length C-D = 14cm and A-D = 18cm. What else can we see, we can see that the triangle the angle x is in is and equilateral triangle. Ok we need to use this information to find the the angle x. First you need to do some trigonometry to find the angle at B with in the triangle with the angle x.(its hard to describe without a drawing) . SOHCAHTOA right, so we need TOA because we know the opposite length and the adjacent length. Tan X = 18/14 . then answer divided by Tan and we have the angle B of the triangle B-A-D. Now that we have that and we also know that the angles within a triangle add up to 180. so the triangle with x in it has two angles that equal B and one that equals X. so the next calculation is 180-(B*2) and that will give you the angle X.

Reply 34

harrym96

There's no image attached :frown:

Reply 35

jaker3278

Original post by Forevereuphoria

could i do toa
and
18/14=0.28
then
tan-1(0.28)=
52.1

Thats right your half way there. thats the angle at B,

now all you have to do is 180 - (2*52.1) = X

Thats THE Answer!!! :smile:

The reason for this is because its an equilateral triangle

(edited 9 years ago)

Reply 36

TartarusEnosa

Pythagoras theorem 18^2+14^2= AC^2
AC= sqroot520
AC/2 gives you DX and XC.

DX, XC = sqroot 130

Cosine Rule a^2 = b^2 + c^2 - 2bc Cos A

Let X be A
Therefore DC (14cm) will be a.
The other two sides are b and c.

Rearrange the cosine rule to make Cos A the subject.

Cos A = (b^2 + c^2 - a^2)/2bc

Enter in the figures we have so far.

Cos A = (sqroot130^2 + sqroot130^2 - 14^2)/2*sqroot130*sqroot130
Cos A = 64/260
A= ????

Therefore X is = ???? degrees.

EDIT: Oh right you guys not giving him the answer.
This is a longer method than the others but I find it easier.