In the right triangle shown, what is the cosine of angle C?

Question

sidney18 · Answer

http://www.usatestprep.com/modules/gallery/files/54/5400/5400.png

imqwerty · Answer

try using this formula $$cosine=\frac{ base }{ hypotenuse }$$

sidney18 · Answer

A)
12/13
B)
15/17
C)
5/13
D)
9/17

so the answer would be B?

imqwerty · Answer

no
1st you have to find out x

to find x use the pythagorus theorem

which says-$$(Base)^2 +(Perpendicular)^2=(Hypotenuse)^2$$$$(x+1)^2+(x+15)^2=(x+17)^2$$ this is a quadratic in x
when u solve it you get 2 values of x
x=-7 and x=9

x=-7 will be rejected because then side (x+1) will become -6

so x=9

now when x=9
the base=x+15=9+15=24
the hypotenuse=x+17=9+17=26

now you have the base and hypotenuse now solve it using that formula :)

sidney18 · Answer

OOOOOOHHHHHH thanks i get it now

imqwerty · Answer

:D no prblm
so what answer did u get

sidney18 · Answer

A