In the diagram above, PQT is an isosceles triangle.|PQ| = |QT|, ∠SRQ = 75°, ∠QPT = 25° and PQR is straight line. Find ∠RST
- 20o
- 50o
-
55o
- 70o
- 75o
The correct answer is: C
Explanation
< PTQ = 25° (base angles of an isos. triangle)
\(\therefore\) < PQT = 180° - (25° + 25°) = 130° (sum of angles in triangle PQT)
\(\therefore\) < RST = 130° - 75° = 55° (exterior angle = sum of 2 opp. interior angles)