Help?
In ABC, A is a right angle and M

Question

Help?
In ABC, A is a right angle and M<B  = 45. If AB = 19 feet, what is BC?

a.32.9 ft

b.16.5 ft

c.26.9 ft

d.19.0 ft

hoblos · Answer

|dw:1397407723241:dw|

cos = adjacent / hypotenuse 

for angle B , AB is the adjacent,  and BC is the hypo

so we have  cos45 = AB/BC

can you calculate BC now ?

anonymous · Answer

what is M? this is a 45 45 90 triangle, as such the ratios are x,x, Root2(x) . 
thus the answer would be 19*sqrt(2)

anonymous · Answer

so it would be this->0.70710678118 * 19 right?

hoblos · Answer

if  cos45 = AB/BC

then  BC= AB/cos45 = 19/0.70710678118

anonymous · Answer

oh okay.

hoblos · Answer

then what would be the answer ?

anonymous · Answer

13.435028842420001? so about 13?

hoblos · Answer

|dw:1397408313528:dw|

anonymous · Answer

:/. heh..... i'm not good at these.

anonymous · Answer

plus super tired today. not helping with concentration.

anonymous · Answer

you don't divide you have to multiply by sqrt(2)

hoblos · Answer

$$\cos 45 = AB \div BC $$  $$BC = AB \div \cos45 $$ $$BC = 19 \div 0.70710678118 = ?$$

anonymous · Answer

=26.9

hoblos · Answer

correct

anonymous · Answer

thats wrong hoblos

anonymous · Answer

why?

anonymous · Answer

BC= cos(45) TIMES AB

anonymous · Answer

when you do algebra, to simplify an equation with divisions, you must multiply both sides.

anonymous · Answer

so BC=0.70710678118*19?

anonymous · Answer

oh wait, im sorry, we are doing different things

anonymous · Answer

my apologies, he is using the angular values, I was using a known ration for 45,45,90 triangles.

hoblos · Answer

yeah you were using another method, but both have same answers surely.

anonymous · Answer

.  .
 -

anonymous · Answer

sooo.. still the same answer?

hoblos · Answer

don't be confused @waddlederp 
you found the right answer, it's 26.9

anonymous · Answer

Okay. thanks!

hoblos · Answer

any time :)