h AABC, AB = AC = 15 cm, BC = 18 cm Find cos ZABC) in ZACB
Hint Draw AD perpendicular to BC, then D is mid point BC, so BD =9cm
Pythagoras theorem, AD = 12 cm
Answers
Answered by
2
Answer:
Given, AB=AC=10 and BC=18 cm
cosB=
2AB×BC
AB
2
+BC
2
−AC
2
cosB=
2×10×18
10
2
+18
2
−10
2
cosB=
10
9
cosB=
H
B
=
10
9
Now, cosC=
2AC×BC
AC
2
+BC
2
−AB
2
cosC=
2×10×18
10
2
+18
2
−10
2
cosC=
10
9
Using Pythagoras Theorem,
H
2
=P
2
+B
2
10
2
=P
2
+9
2
P=
19
tanC=
B
P
=
9
19
Thus, tan
2
C−sec
2
B+2=(
9
19
)
2
−(
9
10
)
2
+2
tan
2
C−sec
2
B=
81
19
−
81
100
+2
tan
2
C−sec
2
C+2=
81
−81
+2=1
Answered by
1
Answer:
3/5
Step-by-step explanation:
AB=AC=15, BC=18
Using cosine rule,
AC 2 =BC 2 +AB 2 −2(AB)(BC)cosB
15 2 =18 2 +15 2 −2(15)(18)cosB
cosB= 9/15
cosB= 3/5
(here in 1st and 2nd step 2 means square)
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