(Q11) Consider a triangle △PQR,right angled at R ,in which PQ=29cm units,QR=21cm units ∠PQR =θ,then find the values of
(i)cos
2
θ+sin
2
θ(ii)cos
2
θ-sin
2
θ
R
P
Q
PR
2
=
PR=
units
sin θ=
PR
PQ
=
cos θ=
QR
PQ
=
Now (i)cos
2
θ+sin
2
θ=
PR
2
PQ
2
+
QR
2
PQ
2
=
(ii)cos
2
θ-sin
2
θ=
PR
2
PQ
2
-
QR
2
PQ
2
=
clear