Shortcut key combinations for certain signs?

Somebody tell me shortcut key or key combinations for certain signs used frequently in mathematics:

degree sign (angle, temperature) say 90 degree

exponent 2 (square) small font 2 superscript

exponent 3 (cube) small font 3 superscript

...maybe the same is used for cuberoot before radical sign?

radical sign

is greater than or equal to

is smaller than or equal to

is approximately equal to

is exactly (always) equal to

is not equal to

pi

lambda

meo

nino

alpha

beta

delta

curly

sigma

small triangle sign

angle sign

sign of altitude (a vertical line falling in the center of a horizontal line)

...............

Thanks a lot in advance.