Given: pstr is a parallelogram m∠t: m∠r=1: 3, rd ⊥ ps , rm ⊥ st find: m∠drm

m∠DRM = 45°

Step-by-step explanation:

∵ PSTR is a parallelogram

∴ TS // RP ⇒ opposite sides

∴ m∠T + m∠R = 180° ⇒ (1) (interior supplementary angles)

∵ m∠T : m∠R = 1 : 3

∴ m∠R = 3 m∠T ⇒ (2)

- Substitute (2) in (1)

∴ m∠T + 3 m∠T = 180

∴ 4 m∠T = 180

∴ m∠T = 180 ÷ 4 = 45°

∴ m∠R = 3 × 45 = 135°

∵ m∠R = m∠S ⇒ opposite angles in a parallelogram

∴ m∠S = 135°

∵ RD ⊥ PS

∴ m∠RDS = 90°

∵ RM ⊥ ST

∴ m∠RMS = 90°

- In quadrilateral RMSD

∵ m∠S = 135°

∵ m∠RDS = 90°

∵ m∠RMS = 90°

∵ The sum of measure of the angles of RMSD = 360°

∴ m∠DRM = 360 - ( 135 + 90 + 90) = 45°

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