solution-of-triangles-7
Q-7: Solve in terms of K where K is perimeter of D ABC.
Solution:
Here,
Q-8: Find the sides and angles of the pedal triangle.
Solution:
Fig (19)
Since the angle PDC and PEC are right angles, the points P, E, C and D lie on a circle.
\ÐPDE = ÐPCE = 90-A
Similarly P, D, B and F lie on a circle and therefore
ÐPDF = ÐPBF = 90-A
Hence ÐFDE = 180-2A
Similarly ÐPEF = 180-2B
ÐEFD = 180-2C
Also from triangle AEF we have
Q-9: Prove that in a DABC
Solution:
L.H.S =
Q-10: Find the radii of the inscribed and the circumscribed circle of a regular polygon of n side
with each side and also find the area of the regular polygon.
Solution:
Fig (20)
Let AB, BC and CD be three successive sides of the polygon and O be the center of both
the incircle and the circumcircle of the
polygon.
If a be a side of the polygon, we have a=BC=2BL=2RSinBOL =
Now the area of the regular polygon = n times the area of the DOBC
Q-11: If a1b and A are given in a triangle and c1, c2 are the possible values of the third side,
prove that
Solution:
Q-12: Prove that in a triangle the sum of exradii exceeds the inradius by twice the diameter of
the circumcircle.or prove that r1+r2+r3 = r+4R.
Solution: Let the exradii be r1, r2, r3 and inradius = r, circum radius = R.
Then we have to prove that r1+r2+r3 = r+4R.
Now,
Medium
Q-1:
In a DABC the angles A, B, C are in A.P show that
Solution:
Here, A, B, C are in A.P So B=A-a; C=A-2a
Also
Q-2: If in a DABC, CosA.CosB+SinA.SinB.SinC = 1, Show that a: b: c = 1:1:Ö2
Solution: Given relation yields,