Answer:
The focal length of the given spherical mirror is 20cm.
Explanation:
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Answer:

Explanation:
As we know that magnitude of two vectors is given as

here we know that
A = magnitude of vector A
B = magnitude of vector B
= angle between two vectors
so here we know that
A = 30 units
B = 40 units
angle = 90 degree
so we have



Answer:
The answer is: B. -487 ..............