Answer:
AC = XY
Step-by-step explanation:
A triangle is a polygon with three sides and three angles. The types of triangles are scalene triangle, equilateral triangle, right angled triangle and obtuse triangle.
Two triangles are said to be congruent if all the three sides and three angles of one triangle is equal to the three sides and three angles of the other triangle.
In Δ ABC and ΔXYZ ,∠B=∠X=90. This means that triangle ABC and triangle XYZ are right angled triangle since one of their angles is 90 degrees.
The hypotenuse is the side opposite to right angle (90 degrees).
Therefore AC is the hypotenuse of triangle ABC and YZ is the hypotenuse of triangle XYZ.
If the hypotenuse and one leg of a right angled triangle is equal to the hypotenuse and leg of another right angled triangle, then the two triangles are congruent by RHS rule.
Since BC = XY, for Δ ABC congruent to ΔXYZ by R.H.S condition, the hypotenuse have to be equal, i.e. AC = XY
we have that 
. This means that period of cosine function is π. Then from the formula for period 
you obtain that 
and b=2. 
. If f(0)=4, then 
and, respectively, a=4.
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