Posted by **Maram** on Tuesday, April 19, 2011 at 12:10pm.

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

- Algebra 1 -
**Henry**, Thursday, April 21, 2011 at 3:31pm
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 = 169-100 = 69,

X = 8.3.

cosA = X/r = 8.3/13.

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