Q. 35.0( 4 Votes )
In ΔABC, m∠B = 90, find the measure of the parts of the triangle other than the ones which are given below:
(1) m∠C = 45, AB = 5
(2) m∠A = 30, AC = 10
(3) AC = 6√2, BC = 3√6
(4) AB = 4, BC = 4
Answer :
(1) If ∠C = 45 and ∠B = 90
⇒ ∠A = 45 (angle sum property of a triangle)
∠A = ∠C
⇒ AB = BC (sides opposite to equal angles)
and since, AB = 5
⇒ BC = 5
and by Pythagoras theorem
AB2 + BC2 = AC2
⇒ 52 + 52 = AC
⇒ AC = 5√2
(2) if ∠A = 30 and ∠B = 90
⇒ ∠C = 60 (Angle sum property of triangle)
put the known values
also,
(3)
⇒ ∠C = 30
⇒ ∠A = 60 (by angle sum property)
also, by Pythagoras theorem
AB2 = AC2 – BC2
⇒ AB = 3√2
(4) Since ∠B = 90
⇒ AB2 + BC2 = AC2
substituting AC = 4 and BC = 4
we get
AC = 4√2
Also since, AB = BC
⇒ ∠A = ∠C (angles opposite to equal sides of the same triangle)
∵ ∠B = 0
⇒ ∠A = ∠C = 45 (Angle sum property)
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(1) m∠C = 45, AB = 5
(2) m∠A = 30, AC = 10
(3) AC = 6√2, BC = 3√6
(4) AB = 4, BC = 4
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