In triangle CAT, the measure of angle C= 90 degrees, AC =5, CT=12, and AT=13, What is the cosine of angle T?

Question

2731 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-05-12T23:44:34

enter image source here

#cosT=12/13=0.923#

Answer 2 · 2015-05-12T23:46:22

#cosT=0.92# to two s.f.

Method
enter image source here
Apply the cosine rule for angle T and the side CA

#=> (AC)^2=(AT)^2+(CT)^2-2(AT)(CT)cosT#

#=>cosT=((AC)^2-(AT)^2-(CT)^2)/(-2(AT)(CT))#

#=>cosT=(25-169-144)/(-2*13*12)=0.92#