A right angle equals 90
90
An acute angle is less than 90
45
An obtuse angle is more than 90
135
Angles are complementary when they
add up to 90
45
45
Angles are supplementary when they
add up to 180
45
135
A straight angle equals 180
180
Vertical Angles are the angles opposite
each other when two lines cross
a = 135
c = 45
Supplementary angles: a and b
a and c
c and d
b and d
b = 45
d = 135
Opposite angles are equal:
a=d
b=c