A simple problem for a simple day

Geometry Level 4

Angles α = a ° , β = b ° \alpha = a°, \beta = b° and γ = c ° \gamma = c° belong to a triangle and satisfy the following:

  1. sin α × sin β × sin γ = 3 3 8 \sin{\alpha} \times \sin{\beta} \times \sin{\gamma} = \frac{3 - \sqrt{3}}{8}

  2. sin 2 α + sin 2 β = 3 2 \sin{2\alpha} + \sin{2\beta} = \frac{3}{2}

Sumit your solution in form: c + R ( a , 17 ) + R ( b , 17 ) c + R(a, 17) + R(b, 17) .

Function R ( x , y ) R(x, y) has a value of remainder when x x is divided by y y .

e. g. R ( 13 , 4 ) = 1 R(13, 4) = 1 , R ( 45 , 5 ) = 0 R(45, 5) = 0

Inspiration: Solution section.


The answer is 146.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Rishabh Jain
Jan 23, 2016

Observatory Solution \color{forestgreen}{\Large\text{Observatory Solution}} 3 3 8 = ( 1 2 ) ( 3 1 2 2 ) ( 3 2 ) = ( sin 45 ) ( sin 15 ) ( s i n 120 ) \dfrac{3-\sqrt{3}}{8}=(\dfrac{1}{\sqrt2})(\dfrac{\sqrt3-1}{2\sqrt2})(\dfrac{\sqrt3}{2})=(\sin 45)(\sin 15)(\ sin 120) Using the second equation we can easily verify α = 45 , β = 15 \alpha = 45, \beta = 15 and hence γ = 120 \gamma=120 Formal Solution \color{forestgreen}{\Large\text{Formal Solution}} Using sin2A+sin2B+sin2C=4sinA sinB sinC given A+B+C= π \small{\color{#69047E}{\text{Using sin2A+sin2B+sin2C=4sinA sinB sinC given A+B+C=}\pi}} sin 2 α + sin 2 β + sin 2 γ = 4 sin α × sin β × sin γ = 4 3 3 8 \sin{2\alpha} + \sin{2\beta} + \sin2\gamma=4 \sin{\alpha} \times \sin{\beta} \times \sin{\gamma} =4 \frac{3 - \sqrt{3}}{8} 2 3 + sin γ = 3 3 2 \Rightarrow \dfrac{2}{3}+\sin\gamma=\frac{3 - \sqrt{3}}{2} γ = 120 \Rightarrow \gamma=120 and solving the equations we get the previously obtained values i.e a=45, b=15 and c=120. R(a,17)=11,R(b,17)=15. Hence, 120 + 11 + 15 = 146 \Large 120+11+15=146

Great observatory solutions. Up voted.!

Priyanshu Mishra - 5 years, 4 months ago

Log in to reply

Thanks!! \large\color{#D61F06}{\text{Thanks!!}}

Rishabh Jain - 5 years, 4 months ago
Milan Milanic
Jan 23, 2016

Inspiration: This problem belongs to DMS ("Drustvo Matematicara Srbije" - Mathematic Society of Serbia) and was on today's math contest. I really like this problem and therefore, I have decided to post it.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...