Solve Triangle

Geometry Level 1

I n t r i a n g l e A B C F i n d x a n d y In\quad triangle\quad \triangle ABC\quad \\ Find\quad \angle x\quad and\quad \angle y

45 and 45 50 and 40 60 and 30 35 and 55

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3 solutions

Gabriel Gomes
Aug 25, 2014

You could simple use the Law of Sines, applying the relation of A ^ \hat { A } with its opposite side and C ^ \hat { C } with the hypotenuse.

4 sin y = 8 sin 90 \frac{4}{\sin y} = \frac{8}{\sin 90}

Therefore, we have that

4 = 8 × sin y 4 = 8 \times \sin y

1 2 = sin y \frac{1}{2} = \sin y

It is easy to see that 1 2 = sin 30 \frac{1}{2} = \sin 30 , so A ^ = 30 º \hat { A } =30º .

Now, to find B ^ \hat { B } , we can use the Sum of Interior Angles of a triangle.

A ^ + B ^ + C ^ = 180 º \hat { A }+ \hat { B }+ \hat { C } = 180º

30 º + B ^ + 90 º = 180 30º + \hat { B }+ 90º = 180

B ^ = 60 º \hat { B } = 60º

Finally, we have that x = 60 º x = 60º and y = 30 º y = 30º .

cos x = 4 8 \cos~x=\dfrac{4}{8} \implies x = cos 1 ( 4 8 ) = x=\cos^{-1}\left(\dfrac{4}{8}\right)= 60 \color{#D61F06}\boxed{60}

sin y = 4 8 \sin~y=\dfrac{4}{8} \implies y = sin 1 ( 4 8 ) = y=\sin^{-1}\left(\dfrac{4}{8}\right)= 30 \color{#D61F06}\boxed{30}

Rohaan Nadeem
Aug 3, 2014

Easiest question so far! Since the hypotenuse is 8 units and base is 4 units in length,perpendicular is calculated to be 7.07 units via Pythagoras Theorem. Using Sine rule: Sin x =(1/8)x7.07 x=62° Therefore y=28° When rounded to nearest 10ths, x=60° y=30°

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