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secondary 3 | A Maths
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MM
MM

secondary 3 chevron_right A Maths chevron_right Singapore

Please help to solve

Date Posted: 3 weeks ago
Views: 19
J
J
3 weeks ago
Use formula

Area of △ = ½ab sin c


½ (3 + √2)(b + 3√2) sin45° = 11/2 + 3√2

½ (3b + 9√2 + b√2 + 3(2) ) (√2 / 2) = 11/2 + 3√2

3b√2 / 4 + 9/2 + b/2 + 3√2 /2 = 11/2 + 3√2

9/2 + b/2 + (3b/4 + 3/2 ) √2 = 11/2 + 3√2

Comparing coefficients,

9/2 + b/2 = 11/2
b/2 = 11/2 - 9/2 = 1
b = 2

Or



Comparing coefficients,


3b/4 + 3/2 = 3

3b/4 = 3 - 3/2 = 3/2

b = 3/2 x 4/3 = 2
MM
MM
3 weeks ago
I tried it but it did not work
snell
Snell
3 weeks ago
0.5 x (3+√2) x (b + 3√2) x sin 45deg
= 0.5 x (3b + 9√2 + b√2 + 6) x 1/√2
= 0.5 x [3b+6 + (9+b)√2] x 1/√2
= 0.5 x [3b+b√2+ 6 +9√2] x 1/√2
= 0.5 x [3b/√2+b+ 6/√2 +9]
or
= 0.5 x [b + 9 + 6/√2 + 3b/√2]


(b + 9)/2 = 11/2
b = 2 (shown)


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J
J
3 weeks ago
Refer to my edited working above. If there's any doubts feel free to ask.
Eric Nicholas K
Eric Nicholas K
3 weeks ago
Will write this up later on paper
MM
MM
3 weeks ago
I am understood

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Jack
Jack's answer
34 answers (A Helpful Person)
1st
Use sine rule