Algebra 1
posted by Maram .
In triangle ABC ,if <A and <B are acute angles, and sin A=10/13 what is the value of cos A?

sinA = 10/13.
This is assumed to be a rt triangle.
sinA = 10/13 = Y/r,
X^2+Y^2 = r^2,
X^2+(10)^2 = (13)^2,
x^2 = 169100 = 69,
X = 8.3.
cosA = X/r = 8.3/13.
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