Rlly easy GCSE sine/cosine

[red cedar]

I just need to know where they got the 22.8 and 54 from, I'm lost

Rlly easy GCSE sine/cosine

[clever shore]

area of any triangle is 1/2 ab sin C

where C is the angle between the two other sides

so 1/2 × 6.7 × 8.4 × sin theta = 22.8

rearrange and solve for theta to find the angle given

[red cedar]

How would I do that?

I've never really understood rearranging formulas

[clever shore]

what do you think the first step is

we want just theta

or, whatever variable you want to use

to represent the angle

[red cedar]

Do you switch times to divide?

[clever shore]

we will do, but what can we do with the 1/2 × 6.7 × 8.4?

[red cedar]

Not sure

[clever shore]

you do 1/2 × 6.7 × 8.4

we have stuff we can times

so we just do it

[red cedar]

So that gives 28.14

[clever shore]

so now we have 28.14 × sinθ = 22.8

how could I get just sinθ?

(btw, θ is the symbol for theta)

[red cedar]

Wait no you swap places right?

So sin theta= 28.14x22.8??

[clever shore]

no

that doesn't work

if I write it like sinθ×28.14=22.8

that might be more clear

[red cedar]

Wait then we divide them?

[clever shore]

yes

[red cedar]

So does 28.14 go on top?

[clever shore]

then, sinθ=22.8/28.14

[clever shore]

no

think of how dividing works in general

the one you're dividing by goes on the denominator

[red cedar]

But that comes out as 0.8102345416

So there has to be something else to make it bigger

[clever shore]

yes

were getting to it

[red cedar]

Oh okay

[clever shore]

we want θ

we have sinθ

[red cedar]

Sin-1

?

[clever shore]

to get rid of the sin, we do sin^-1

yea

[red cedar]

That gives 54.11885309

[clever shore]

so θ=sin^-1(22.8/28.14)

[clever shore]

which if you round

[red cedar]

54

[clever shore]

is 54

which is what's on the ms

[red cedar]

Ohhhhhhhh

Thank you so much

[clever shore]

np, I'm recommend you just revise some rearranging stuff

rearranging equations

cus it's a vital skill to be fluent in

[red cedar]

Yeah, I do try some of them I can just see but others takes a bit of time to get whats happening, especially when there's multiple triangles going on my head gers confused

[clever shore]

na ur all good

ur only y9

aswell

give it time and you'll be better

[red cedar]

I'm now in Yr 10 idk how to change it lol got my maths gcse's in 2/3 months

[clever shore]

#829409053993599076

Well if you have any other questions u need help w

ping me or the maths mentor role

and me/someone will help you

[red cedar]

Alright thanks so much

[clever shore]

no worries

[red cedar]

Sorry lol, the next part doesn't add right for me, square root of DB² = 6.7²+8.4²-(2x6.7x8.4xcos(54)) = 9.85457274 for me but the mark scheme says 7

[clever shore]

,w sqrt(6.7²+8.4²-2×6.7×8.4×cos54.1188)

(using θ cus we already know what θ is)

[red cedar]

Isn't that the same as I did?

[gloomy blade]

Results provided by WolframAlpha

Click here to refine your query online
Upgrade to WolframAlpha Pro!

Requested by mot_.

[red cedar]

What

Whyd that pop up

[clever shore]

what is wolfram on

[red cedar]

Idk

[clever shore]

cus I made it pop up

I used a bot we have

[red cedar]

Oh is it cause I put cos54 not cos54.1188??

Hold on nevermind

I've gotten 9 from somewhere and idk where but now my calculators saying 7

[clever shore]

@red cedar

you did smth

[red cedar]

No idea what I did

Anyways hopefully it works now

[clever shore]

probably the brackets in the -(bit)

[red cedar]

Prob

The perimeter is in cm right