In a right angled triangle ABC, C = 90° then cos? A + cos²B =
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Answer:
As ∠C=90
o
∴cosA=
AB
BC
cosB=
AB
AC
cos
2
A+cos
2
B=
AB
2
BC
2
+
AB
2
AC
2
=
AB
2
BC
2
+AC
2
From △ABC,
By Pythagoras Theorem,
AB
2
=AC
2
+BC
2
⇒cos
2
A+cos
2
B=
AB
2
AB
2
∴cos
2
A+cos
2
B=1
solution
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