### Video Transcript

Find the value of cos π΅.

Looking at this triangle, thereβs a
few things we can note. The large triangle on the outside is
an isosceles triangle, and both of the smaller interior triangles are right
triangles. The line π΄π· creates the height of
the outer isosceles triangle. It also tells us something
else. Line π΄π· creates a perpendicular
line to line πΆπ΅. And that means that it bisects line
πΆπ΅. Line πΆπ΅ can be broken up into two
equal halves, both equal to 15 centimeters.

Cos of π΅ can be found by looking
at this interior right triangle. When weβre dealing with right
triangle trig, cos of π equals the adjacent side length over the hypotenuse side
length. Cos of π΅ must equal its adjacent
side length, 15, over its hypotenuse side length, 34. Cos of angle π΅ equals 15 over
34.