Sine cosine rule

Heya just needed abit of help and explantion on how i can work this out. i tried the forumlas but they didnt work.

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For this question, you don't need to use the sine or cosine rules. Instead, since you have the area of the triangle, you can use the two lengths and area to rearrange the formula for the area of a non right angled to find the angle.

Hope this helped :smile:

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Reply 2

JN17

If 1/2absin(c) = 4, then 1/2 (4.3)(4.3)sin(x) = 4, rearrange for sin(x).
Once you have one value for x(probably from a calculator), look at the graph of y= sin(x) to see other values of x that give the same value of sin(x) (whilst still having x less than 180 degrees so it can make a triangle)

Reply 3

NotNotBatman

Original post by z_o_e

Heya just needed abit of help and explantion on how i can work this out. i tried the forumlas but they didnt work.

Use the area of a triangle =

\frac{1}{2}absinC

Nice MyMaths lmao

mymaths has a history of shwoing the answers as wrong when they are actually right

Reply 6

BobBobson

Original post by AnnemarieV

mymaths has a history of shwoing the answers as wrong when they are actually right

I once put in 13 years 0 months as an answer to a mymaths question and it marked it wrong saying the answer is 12 years 12 months

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Reply 7

z_o_e

Original post by BobBobson

I once put in 13 years 0 months as an answer to a mymaths question and it marked it wrong saying the answer is 12 years 12 months

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Heya can you help me on this question please

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Reply 8

z_o_e

Original post by JN17

Thank you x

I need help on the above

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Reply 9

BobBobson

Original post by z_o_e

Heya can you help me on this question please

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What help do you need? You seemed to have solved it. All you need to do is put that fraction into the inverse of cos function on your calculator.
On most calculators it looks like cos to the power of -1.

Reply 10

z_o_e

Original post by BobBobson

It said error

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Reply 11

z_o_e

Also for this
I need to find ourt angle BAC
I don't understand what angle is that

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Reply 12

JN17

Original post by z_o_e

Thank you x

I need help on the above

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As the person above said, you've done it, just simplify the squares and fraction and do cos-1(that answer) for the angle A

Reply 13

BobBobson

Original post by z_o_e

It said error

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It works fine when I put it into my calculator. What type of error is it?

Reply 14

z_o_e

Original post by BobBobson

It works fine when I put it into my calculator. What type of error is it?

Got it! !!

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Reply 15

z_o_e

Original post by BobBobson

It works fine when I put it into my calculator. What type of error is it?

For this I need to find BAC angle what angle is that?

I dont understand questions like that the wording BAC do I find angle B AND A AND C

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Reply 16

z_o_e

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Reply 17

BobBobson

Original post by z_o_e

For this I need to find BAC angle what angle is that?

I dont understand questions like that the wording BAC do I find angle B AND A AND C

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When an angle is written as "BAC" for example, it means the angle between the line BA and AC, or what you wrote down as simply A. People write it like that to avoid ambiguity. It doesn't mean to find all three angles.