△ ABC is right angle triangle at A, AB=11, BC=13, AC=8. Write sin A, cos C, tan A 
Lets draw the right angle triangle with the above mentioned details
Given thing are
Right angle at A
Theta Angle at B (As mentioned in statement sin B, tan B that means angle B should be taken as Theta)
Hypotenuse : BC = 13
Opposite Side : AC = 8 (Opposite to ∠ Θ)
Adjacent Side : AB = 11 (Adjacent to ∠ Θ)
Sin A = Opposite Side/Hypotenuse = 8/13
Tan A = Opposite Side/Adjacent = 8/11
For Cos the Theta Angle is at C (As mentioned in statement "Cos C" that means angle C should be taken as Theta)
As cos angle is now C, the adjacent side and opposite side of the triangle will be as below
You will see that Theta angle is now at A, So
Hypotenuse : BC = 13
Opposite Side : AB = 11 (Opposite to ∠ Θ)
Adjacent Side : AC = 8 (Adjacent to ∠ Θ)
So, cos C = Adjacent Side/Hypotenuse = 8/13

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