no.
The equivalence is 225 50 R18 so that the diameter may be the same.
Simply multiply the diameter times pi.
No, the 245/40-17 is 2.03" smaller in diameter. This is not acceptable. You speedometer will be 4.9 mph too fast at 60 mph.
what is the diameter difference from a 205/65/16 vs. 225/60/16
diameter = 30 units area = 225*pi square units
225ºF = 107.22ºC
Yes, you can There will be about a 5% decrease in the tire diameter. 225 65 tires are 225mm wide and 146.25mm in height (65% of the width), while 215 60 tires are 129mm tall, which will affect the odometer and speedometer. When your speedometer reads 60 mph, you'll actually be traveling closer to 57 mph. Replacing the 225 65 tires with 215 70 tires would keep the diameter almost the same (150.5mm).
An acute angle that is 1/4 of a right angle
Of course you can but the question is should you. It is never recommended to go over 3% difference in overall diameter. The 225/40-18 will be 3.43% smaller in overall diameter. Your speedometer will read 62.1 at a true 60 mph. I would not recommend this swap.
(sqrt 2) / 2
The given measure, 225*pi cm is a linear measure so it cannot refer to the area. It could refer to the radius or the circumference of the circles, or the length of an arc or a segment of the circle. It could, of course refer to something else, but then the task of finding the diameter is near impossible. If it is the length of an arc or a segment, you require further information. Since that is not provided, perhaps one can assume that the measure does not refer to either. That leaves the radius or the circumference. If the radius is 225*pi then the diameter is simply 2*radius = 450*pi cm. If the circumference is 225*pi, then the diameter is circumference/pi = 225 cm.
That's pretty close. The 235/60-18 has a diameter of 29.1" (739.2mm) and the 225/65-18 has a diameter of 29.52" (749.7mm) and a true 60.85mph on a speedometer reading of 60