SOLUTION: In (triangle)ABC, if A and B are acute angles, and sin A =10/13 , what is the value of cos A ? please help, need to know how to do this on my calculator too. thank you

Algebra ->  Triangles -> SOLUTION: In (triangle)ABC, if A and B are acute angles, and sin A =10/13 , what is the value of cos A ? please help, need to know how to do this on my calculator too. thank you      Log On


   

Question 30116: In (triangle)ABC, if A and B are acute angles, and sin A =10/13 ,
what is the value of cos A ?
please help, need to know how to do this on my calculator too.
thank you
Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
In triangle AB, A and B are acute angles so. AC and BC are right angles.
Sin A = 10/13
13 is the hypotenuse side and 10 is the opposite side.
To find cos A.
From pythagorean thereom:



b=8.3

SO the value for cos A is 8.3/13
cos A=0.63 take the inverse sine of cosine:
cos A=51 degrees.
PAul.